Communication system, user apparatus, and base station

ABSTRACT

A communication system includes a user apparatus; and a base station including a distributed unit (DU) configured to wirelessly communicate with the user apparatus and a central unit (CU) connected to the distributed unit. The base station including the CU and the DU supports packet duplication, and the DU notifies the user apparatus of starting the packet duplication.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. application Ser. No. 17/394,529 filedAug. 5, 2021, which is a continuation of U.S. application Ser. No.16/633,307 (now U.S. Pat. No. 11,116,025) filed Jan. 23, 2020, theentire contents of which are incorporated herein by reference. U.S.application Ser. No. 16/633,307 is a National Stage of PCT/JP2018/029566filed Aug. 7, 2018, which claims the benefit of priority under 35 U.S.C.§ 119 from Japanese Application No. 2017-152932 filed Aug. 8, 2017.

TECHNICAL FIELD

The present invention relates to a communication system, etc., in whichradio communication is performed between a communication terminal devicesuch as a user equipment device and a base station device.

BACKGROUND ART

The 3rd generation partnership project (3GPP), the standard organizationregarding the mobile communication system, is studying communicationsystems referred to as long term evolution (LTE) regarding radiosections and system architecture evolution (SAE) regarding the overallsystem configuration including a core network and a radio access networkwhich is hereinafter collectively referred to as a network as well (forexample, see Non-Patent Documents 1 to 5). This communication system isalso referred to as 3.9 generation (3.9 G) system.

As the access scheme of the LTE, orthogonal frequency divisionmultiplexing (OFDM) is used in a downlink direction and single carrierfrequency division multiple access (SC-FDMA) is used in an uplinkdirection. Further, differently from the wideband code division multipleaccess (W-CDMA), circuit switching is not provided but a packetcommunication system is only provided in the LTE.

The decisions taken in 3GPP regarding the frame configuration in the LTEsystem described in Non-Patent Document 1 (Chapter 5) are described withreference to FIG. 1 . FIG. 1 is a diagram illustrating the configurationof a radio frame used in the LTE communication system. With reference toFIG. 1 , one radio frame is 10 ms. The radio frame is divided into tenequally sized subframes. The subframe is divided into two equally sizedslots. The first and sixth subframes contain a downlink synchronizationsignal per radio frame. The synchronization signals are classified intoa primary synchronization signal (P-SS) and a secondary synchronizationsignal (S-SS).

Non-Patent Document 1 (Chapter 5) describes the decisions by 3GPPregarding the channel configuration in the LTE system. It is assumedthat the same channel configuration is used in a closed subscriber group(CSG) cell as that of a non-CSG cell.

A physical broadcast channel (PBCH) is a channel for downlinktransmission from a base station device (hereinafter may be simplyreferred to as a “base station”) to a communication terminal device(hereinafter may be simply referred to as a “communication terminal”)such as a user equipment device (hereinafter may be simply referred toas a “user equipment”). A BCH transport block is mapped to foursubframes within a 40 ms interval. There is no explicit signalingindicating 40 ms timing.

A physical control format indicator channel (PCFICH) is a channel fordownlink transmission from a base station to a communication terminal.The PCFICH notifies the number of orthogonal frequency divisionmultiplexing (OFDM) symbols used for PDCCHs from the base station to thecommunication terminal. The PCFICH is transmitted per subframe.

A physical downlink control channel (PDCCH) is a channel for downlinktransmission from a base station to a communication terminal. The PDCCHnotifies of the resource allocation information for downlink sharedchannel (DL-SCH) being one of the transport channels described below,resource allocation information for a paging channel (PCH) being one ofthe transport channels described below, and hybrid automatic repeatrequest (HARQ) information related to DL-SCH. The PDCCH carries anuplink scheduling grant. The PDCCH carries acknowledgement(Ack)/negative acknowledgement (Nack) that is a response signal touplink transmission. The PDCCH is referred to as an L1/L2 control signalas well.

A physical downlink shared channel (PDSCH) is a channel for downlinktransmission from a base station to a communication terminal. A downlinkshared channel (DL-SCH) that is a transport channel and a PCH that is atransport channel are mapped to the PDSCH.

A physical multicast channel (PMCH) is a channel for downlinktransmission from a base station to a communication terminal. Amulticast channel (MCH) that is a transport channel is mapped to thePMCH.

A physical uplink control channel (PUCCH) is a channel for uplinktransmission from a communication terminal to a base station. The PUCCHcarries Ack/Nack that is a response signal to downlink transmission. ThePUCCH carries a channel quality indicator (CQI) report. The CQI isquality information indicating the quality of received data or channelquality. In addition, the PUCCH carries a scheduling request (SR).

A physical uplink shared channel (PUSCH) is a channel for uplinktransmission from a communication terminal to a base station. An uplinkshared channel (UL-SCH) that is one of the transport channels is mappedto the PUSCH.

A physical hybrid ARQ indicator channel (PHICH) is a channel fordownlink transmission from a base station to a communication terminal.The PHICH carries Ack/Nack that is a response signal to uplinktransmission. A physical random access channel (PRACH) is a channel foruplink transmission from the communication terminal to the base station.The PRACH carries a random access preamble.

A downlink reference signal (RS) is a known symbol in the LTEcommunication system. The following five types of downlink referencesignals are defined as: a cell-specific reference signal (CRS), an MBSFNreference signal, a data demodulation reference signal (DM-RS) being aUE-specific reference signal, a positioning reference signal (PRS), anda channel state information reference signal (CSI-RS). The physicallayer measurement objects of a communication terminal include referencesignal received powers (RSRPs).

The transport channels described in Non-Patent Document 1 (Chapter 5)are described. A broadcast channel (BCH) among the downlink transportchannels is broadcast to the entire coverage of a base station (cell).The BCH is mapped to the physical broadcast channel (PBCH).

Retransmission control according to a hybrid ARQ (HARQ) is applied to adownlink shared channel (DL-SCH). The DL-SCH can be broadcast to theentire coverage of the base station (cell). The DL-SCH supports dynamicor semi-static resource allocation. The semi-static resource allocationis also referred to as persistent scheduling. The DL-SCH supportsdiscontinuous reception (DRX) of a communication terminal for enablingthe communication terminal to save power. The DL-SCH is mapped to thephysical downlink shared channel (PDSCH).

The paging channel (PCH) supports DRX of the communication terminal forenabling the communication terminal to save power. The PCH is requiredto be broadcast to the entire coverage of the base station (cell). ThePCH is mapped to physical resources such as the physical downlink sharedchannel (PDSCH) that can be used dynamically for traffic.

The multicast channel (MCH) is used for broadcasting the entire coverageof the base station (cell). The MCH supports SFN combining of multimediabroadcast multicast service (MBMS) services (MTCH and MCCH) inmulti-cell transmission. The MCH supports semi-static resourceallocation. The MCH is mapped to the PMCH.

Retransmission control according to a hybrid ARQ (HARQ) is applied to anuplink shared channel (UL-SCH) among the uplink transport channels. TheUL-SCH supports dynamic or semi-static resource allocation. The UL-SCHis mapped to the physical uplink shared channel (PUSCH).

A random access channel (RACH) is limited to control information. TheRACH involves a collision risk. The RACH is mapped to the physicalrandom access channel (PRACH).

The HARQ is described. The HARQ is the technique for improving thecommunication quality of a channel by combination of automatic repeatrequest (ARQ) and error correction (forward error correction). The HARQis advantageous in that error correction functions effectively byretransmission even for a channel whose communication quality changes.In particular, it is also possible to achieve further qualityimprovement in retransmission through combination of the receptionresults of the first transmission and the reception results of theretransmission.

An example of the retransmission method is described. If the receiverfails to successfully decode the received data, in other words, if acyclic redundancy check (CRC) error occurs (CRC=NG), the receivertransmits “Nack” to the transmitter. The transmitter that has received“Nack” retransmits the data. If the receiver successfully decodes thereceived data, in other words, if a CRC error does not occur (CRC=OK),the receiver transmits “AcK” to the transmitter. The transmitter thathas received “Ack” transmits the next data.

The logical channels described in Non-Patent Document 1 (Chapter 6) aredescribed. A broadcast control channel (BCCH) is a downlink channel forbroadcast system control information. The BCCH that is a logical channelis mapped to the broadcast channel (BCH) or downlink shared channel(DL-SCH) that is a transport channel.

A paging control channel (PCCH) is a downlink channel for transmittingpaging information and system information change notifications. The PCCHis used when the network does not know the cell location of acommunication terminal. The PCCH that is a logical channel is mapped tothe paging channel (PCH) that is a transport channel.

A common control channel (CCCH) is a channel for transmission controlinformation between communication terminals and a base station. The CCCHis used in a case where the communication terminals have no RRCconnection with the network. In the downlink direction, the CCCH ismapped to the downlink shared channel (DL-SCH) that is a transportchannel. In the uplink direction, the CCCH is mapped to the uplinkshared channel (UL-SCH) that is a transport channel.

A multicast control channel (MCCH) is a downlink channel forpoint-to-multipoint transmission. The MCCH is used for transmission ofMBMS control information for one or several MTCHs from a network to acommunication terminal. The MCCH is used only by a communicationterminal during reception of the MBMS. The MCCH is mapped to themulticast channel (MCH) that is a transport channel.

A dedicated control channel (DCCH) is a channel that transmits dedicatedcontrol information between a communication terminal and a network on apoint-to-point basis. The DCCH is used when the communication terminalhas an RRC connection. The DCCH is mapped to the uplink shared channel(UL-SCH) in uplink and mapped to the downlink shared channel (DL-SCH) indownlink.

A dedicated traffic channel (DTCH) is a point-to-point communicationchannel for transmission of user information to a dedicatedcommunication terminal. The DTCH exists in uplink as well as downlink.The DTCH is mapped to the uplink shared channel (UL-SCH) in uplink andmapped to the downlink shared channel (DL-SCH) in downlink.

A multicast traffic channel (MTCH) is a downlink channel for trafficdata transmission from a network to a communication terminal. The MTCHis a channel used only by a communication terminal during reception ofthe MBMS. The MTCH is mapped to the multicast channel (MCH).

CGI represents a cell global identifier. ECGI represents an E-UTRAN cellglobal identifier. A closed subscriber group (CSG) cell is introducedinto the LTE, and the long term evolution advanced (LTE-A) and universalmobile telecommunication system (UMTS) described below.

The closed subscriber group (CSG) cell is a cell in which subscriberswho are allowed to use are specified by an operator (hereinafter, alsoreferred to as a “cell for specific subscribers”). The specifiedsubscribers are allowed to access one or more cells of a public landmobile network (PLMN). One or more cells to which the specifiedsubscribers are allowed access are referred to as “CSG cell(s)”. Notethat access is limited in the PLMN.

The CSG cell is part of the PLMN that broadcasts a specific CSG identity(CSG ID) and broadcasts “TRUE” in a CSG indication. The authorizedmembers of the subscriber group who have registered in advance accessthe CSG cells using the CSG ID that is the access permissioninformation.

The CSG ID is broadcast by the CSG cell or cells. A plurality of CSG IDsexist in the LTE communication system. The CSG IDs are used bycommunication terminals (UEs) for making access from CSG-related memberseasier.

The locations of communication terminals are tracked based on an areacomposed of one or more cells. The locations are tracked for enablingtracking the locations of communication terminals and callingcommunication terminals, in other words, incoming calling tocommunication terminals even in an idle state. An area for trackinglocations of communication terminals is referred to as a tracking area.

In 3GPP, base stations referred to as Home-NodeB (Home-NB; HNB) andHome-eNodeB (Home-eNB; HeNB) are studied. HNB/HeNB is a base stationfor, for example, household, corporation, or commercial access servicein UTRAN/E-UTRAN. Non-Patent Document 2 discloses three different modesof the access to the HeNB and HNB. Specifically, an open access mode, aclosed access mode, and a hybrid access mode are disclosed.

Further, specifications of long term evolution advanced (LTE-A) arepursed as Release 10 in 3GPP (see Non-Patent Documents 3 and 4). TheLTE-A is based on the LTE radio communication system and is configuredby adding several new techniques to the system.

Carrier aggregation (CA) is studied for the LTE-A system in which two ormore component carriers (CCs) are aggregated to support widertransmission bandwidths up to 100 MHz. Non-Patent Document 1 describesthe CA.

In a case where CA is configured, a UE has a single RRC connection witha network (NW). In RRC connection, one serving cell provides NASmobility information and security input. This cell is referred to as aprimary cell (PCell). In downlink, a carrier corresponding to PCell is adownlink primary component carrier (DL PCC). In uplink, a carriercorresponding to PCell is an uplink primary component carrier (UL PCC).

A secondary cell (SCell) is configured to form a serving cell group witha PCell, in accordance with the UE capability. In downlink, a carriercorresponding to SCell is a downlink secondary component carrier (DLSCC). In uplink, a carrier corresponding to SCell is an uplink secondarycomponent carrier (UL SCC).

A serving cell group of one PCell and one or more SCells is configuredfor one UE.

The new techniques in the LTE-A include the technique of supportingwider bands (wider bandwidth extension) and the coordinated multiplepoint transmission and reception (CoMP) technique. The CoMP studied forLTE-A in 3GPP is described in Non-Patent Document 1.

Furthermore, the use of small eNBs (hereinafter also referred to as“small-scale base station devices”) configuring small cells is studiedin 3GPP to satisfy tremendous traffic in the future. In an exampletechnique under study, a large number of small eNBs is installed toconfigure a large number of small cells, which increases spectralefficiency and communication capacity. The specific techniques includedual connectivity (abbreviated as DC) with which a UE communicates withtwo eNBs through connection thereto. Non-Patent Document 1 describes theDC.

For eNBs that perform dual connectivity (DC), one may be referred to asa master eNB (abbreviated as MeNB), and the other may be referred to asa secondary eNB (abbreviated as SeNB).

The traffic flow of a mobile network is on the rise, and thecommunication rate is also increasing. It is expected that thecommunication rate is further increased when the operations of the LTEand the LTE-A are fully initiated.

For increasingly enhanced mobile communications, the fifth generation(hereinafter also referred to as “5G”) radio access system is studiedwhose service is aimed to be launched in 2020 and afterward. Forexample, in the Europe, an organization named METIS summarizes therequirements for 5G (see Non-Patent Document 5).

The requirements in the 5G radio access system show that a systemcapacity shall be 1000 times as high as, a data transmission rate shallbe 100 times as high as, a data latency shall be one tenth ( 1/10) aslow as, and simultaneously connected communication terminals 100 timesas many as those of the LTE system, to further reduce the powerconsumption and device cost.

To satisfy such requirements, the study of 5G standards is pursued asRelease 14 in 3GPP (see Non-Patent Documents 6 to 10). The techniques on5G radio sections are referred to as “New Radio Access Technology” (“NewRadio” is abbreviated as NR), and the several new techniques are beingstudied (see Non-Patent Documents 11 to 14). Examples of such studiesinclude packet duplication with the DC or multi-connectivity(abbreviated as MC), and split of a gNB into a central unit (CU) and adistributed unit (DU).

PRIOR-ART DOCUMENTS Non-Patent Documents

Non-Patent Document 1: 3GPP TS36.300 V14.3.0

Non-Patent Document 2: 3GPP S1-083461

Non-Patent Document 3: 3GPP TR 36.814 V9.2.0

Non-Patent Document 4: 3GPP TR 36.912 V14.0.0

Non-Patent Document 5: “Scenarios, requirements and KPIs for 5G mobileand wireless system”, ICT-317669-METIS/D1.1

Non-Patent Document 6: 3GPP TR 23.799 V14.0.0

Non-Patent Document 7: 3GPP TR 38.801 V14.0.0

Non-Patent Document 8: 3GPP TR 38.802 V14.1.0

Non-Patent Document 9: 3GPP TR 38.804 V14.0.0

Non-Patent Document 10: 3GPP TR 38.912 V14.0.0

Non-Patent Document 11: 3GPP R2-1700672

Non-Patent Document 12: Draft Report of 3GPP TSG RAN WG2 meeting #98,Hangzhou, China, 15-19 May, 2017

Non-Patent Document 13: 3GPP R2-1704578

Non-Patent Document 14: 3GPP R2-1704660

Non-Patent Document 15: 3GPP TS 36.321 v14.3.0

Non-Patent Document 16: 3GPP R2-1706867

Non-Patent Document 17: 3GPP TS36.322 v14.0.0

Non-Patent Document 18: 3GPP R3-171412

Non-Patent Document 19: 3GPP R2-1706716

Non-Patent Document 20: 3GPP R2-1704836

Non-Patent Document 21: 3GPP R2-1702753

Non-Patent Document 22: 3GPP R2-1704001

Non-Patent Document 23: 3GPP TS36.423 v14.3.0

Non-Patent Document 24: 3GPP TS36.331 v14.3.0

Non-Patent Document 25: 3GPP R2-1704425

Non-Patent Document 26: 3GPP R2-1704420

Non-Patent Document 27: 3GPP R2-167583

Non-Patent Document 28: 3GPP TS37.340 v0.2.0

Non-Patent Document 29: 3GPP TS38.423 v0.1.1

SUMMARY Problems to be Solved by the Invention

In NR, a technology on the packet duplication for duplicating a packetto transmit the identical packets has been proposed to implementcommunication with high reliability and low latency. A method using theCA or the DC has been proposed as a method for implementing the packetduplication. The activation/deactivation of the packet duplication iscontrolled via the MAC signaling.

As a conventional technology, the MAC signaling foractivating/deactivating operations of an SCell to be used for the CA issupported. However, none discloses operations in NR with the CA when theMAC signaling for the packet duplication contends with the MAC signalingfor activating/deactivating the SCell. Thus, upon occurrence of thecontention, the UE does not know how to perform processes for the packetduplication, and thus may malfunction. As a result, the communicationwith high reliability and low latency may not be implemented.

In NR, the MC has been proposed as a technology for implementinghigh-speed communication. Configuring the connection of one UE to onemaster base station and a plurality of secondary base stations has beendiscussed as the MC. However, none discloses, in the MC using two ormore secondary base stations, an architecture including a high-level NWand a method for setting the MC, for example, how to set the two or moresecondary base stations. Thus, the master base station and the secondarybase stations cannot configure the MC. Moreover, the UE cannot implementthe high-speed communication.

In view of the problems, one of the objects of the present invention isto provide a high-speed communication system with high reliability andlow latency, etc., under NR.

Means to Solve the Problems

The present invention provides, for example, a communication systemincluding a communication terminal device, and a base station deviceconfigured to perform radio communication with the communicationterminal device, wherein the communication terminal device is configuredto duplicate a packet and transmit the duplicated packets with carrieraggregation, the base station device is configured to transmit, to thecommunication terminal device, packet duplication control on packetduplication and secondary cell control on a secondary cell to be usedfor the carrier aggregation, and the communication terminal device isconfigured to perform the packet duplication control and the secondarycell control based on priorities defined between the packet duplicationcontrol and the secondary cell control.

The present invention also provides, for example, a communicationterminal device configured to perform radio communication with a basestation device, wherein the communication terminal device is configuredto duplicate a packet and transmit the duplicated packets with carrieraggregation, and the communication terminal device is configured toreceive, from the base station device, packet duplication control onpacket duplication and secondary cell control on a secondary cell to beused for the carrier aggregation, and perform the packet duplicationcontrol and the secondary cell control based on priorities definedbetween the packet duplication control and the secondary cell control.

The present invention also provides, for example, a base station deviceconfigured to perform radio communication with a communication terminaldevice, wherein the communication terminal device is configured toduplicate a packet and transmit the duplicated packets with carrieraggregation, the communication terminal device is configured to performpacket duplication control on packet duplication and secondary cellcontrol on a secondary cell to be used for the carrier aggregation,based on priorities defined between the packet duplication control andthe secondary cell control, and the base station device is configured totransmit the packet duplication control and the secondary cell controlto the communication terminal device.

Effects of the Invention

The present invention can provide a high-speed communication system,etc., with high reliability and low latency under NR.

The objects, features, aspects and advantages of the present inventionbecome more apparent from the following detailed description of thepresent invention when taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the configuration of a radio frame foruse in an LTE communication system.

FIG. 2 is a block diagram showing the overall configuration of an LTEcommunication system 200 under discussion of 3GPP.

FIG. 3 is a block diagram showing the configuration of a user equipment202 shown in FIG. 2 , which is a communication terminal according to thepresent invention.

FIG. 4 is a block diagram showing the configuration of a base station203 shown in FIG. 2 , which is a base station according to the presentinvention.

FIG. 5 is a block diagram showing the configuration of an MME accordingto the present invention.

FIG. 6 is a flowchart showing an outline from a cell search to an idlestate operation performed by a communication terminal (UE) in the LTEcommunication system.

FIG. 7 shows the concept of a cell configuration when macro eNBs andsmall eNBs coexist.

FIG. 8 is a sequence diagram illustrating operations when the UEreceives the MAC signaling for activating packet duplication after aspecified timing due to occurrence of the HARQ retransmission.

FIG. 9 illustrates a protocol configuration in the packet duplicationwith the CA to be performed between a gNB with the CU-DU split and theUE according to the first modification of the first embodiment.

FIG. 10 is a sequence diagram of the packet duplication when the DUdetermines to activate the packet duplication according to the firstmodification of the first embodiment.

FIG. 11 is a sequence diagram of the packet duplication when the CUdetermines to activate the packet duplication according to the firstmodification of the first embodiment.

FIG. 12 is a sequence diagram illustrating operations when the UEreceives the MAC signaling for activating the packet duplication after aspecified timing due to occurrence of the HARQ retransmission accordingto the first modification of the first embodiment.

FIG. 13 is a sequence diagram when a master base station activatesswitching of the packet duplication according to the second embodiment.

FIG. 14 is a sequence diagram when a secondary base station activatesswitching of the packet duplication according to the second embodiment.

FIG. 15 is a sequence diagram illustrating small data transmission fromthe UE to the secondary base station according to the fifth embodiment.

FIG. 16 illustrates an architecture of the MC according to the sixthembodiment.

FIG. 17 illustrates an example sequence for setting the MC according tothe sixth embodiment.

FIG. 18 illustrates the example sequence for setting the MC according tothe sixth embodiment.

FIG. 19 illustrates an example sequence for setting the MC according tothe sixth embodiment.

FIG. 20 illustrates the example sequence for setting the MC according tothe sixth embodiment. FIG. 21 illustrates an architecture and a dataflowwhen a high-level NW is an

NG-CN and a base station is a gNB in NR according to the firstmodification of the sixth embodiment.

FIG. 22 illustrates an architecture of the MC according to the firstmodification of the sixth embodiment.

FIG. 23 is a conceptual diagram illustrating a dataflow when the MC isset for each DRB according to the first modification of the sixthembodiment.

FIG. 24 is a conceptual diagram illustrating a dataflow when the MC isset for each QoS flow according to the first modification of the sixthembodiment.

FIG. 25 is a conceptual diagram illustrating a dataflow in additionallysetting a DRB to which the QoS flow, on which the MC is performed, ismapped according to the first modification of the sixth embodiment.

FIG. 26 illustrates an example sequence for setting the MC for each QoSflow according to the first modification of the sixth embodiment.

FIG. 27 illustrates the example sequence for setting the MC for each QoSflow according to the first modification of the sixth embodiment.

FIG. 28 illustrates an architecture of the MC according to the seventhembodiment.

FIG. 29 illustrates an example sequence for setting the MC with the SCGbearer according to the seventh embodiment.

FIG. 30 illustrates the example sequence for setting the MC with the SCGbearer according to the seventh embodiment.

FIG. 31 illustrates an architecture of the MC with the SCG beareraccording to the first modification of the seventh embodiment.

FIG. 32 is a conceptual diagram illustrating a dataflow when the MC withthe SCG bearer is set for each DRB according to the first modificationof the seventh embodiment.

FIG. 33 illustrates an example sequence for setting the MC with the SCGbearer when the high-level NW is the NG-CN according to the firstmodification of the seventh embodiment.

FIG. 34 illustrates the example sequence for setting the MC with the SCGbearer when the high-level NW is the NG-CN according to the firstmodification of the seventh embodiment.

FIG. 35 illustrates the example sequence for setting the MC with the SCGbearer when the high-level NW is the NG-CN according to the firstmodification of the seventh embodiment.

FIG. 36 is a conceptual diagram illustrating a dataflow when the MC withthe SCG bearer is set for each QoS flow according to the firstmodification of the seventh embodiment.

FIG. 37 illustrates an architecture of the MC according to the eighthembodiment.

FIG. 38 illustrates an example sequence for setting the MC with the SCGsplit bearer according to the eighth embodiment.

FIG. 39 illustrates the example sequence for setting the MC with the SCGsplit bearer according to the eighth embodiment.

FIG. 40 illustrates the example sequence for setting the MC with the SCGsplit bearer according to the eighth embodiment.

FIG. 41 illustrates an architecture of the MC according to the firstmodification of the eighth embodiment.

FIG. 42 is a conceptual diagram illustrating a dataflow when the MC withthe SCG split bearer is set for each DRB according to the firstmodification of the eighth embodiment.

FIG. 43 illustrates an example sequence for setting the MC with the SCGsplit bearer according to the first modification of the eighthembodiment.

FIG. 44 illustrates the example sequence for setting the MC with the SCGsplit bearer according to the first modification of the eighthembodiment.

FIG. 45 illustrates the example sequence for setting the MC with the SCGsplit bearer according to the first modification of the eighthembodiment.

FIG. 46 is a conceptual diagram illustrating a dataflow when the MC withthe SCG split bearer is set for each QoS flow according to the firstmodification of the eighth embodiment.

FIG. 47 illustrates an architecture of the MC according to the ninthembodiment.

FIG. 48 illustrates an architecture of the MC according to the firstmodification of the ninth embodiment.

DESCRIPTION OF EMBODIMENTS The First Embodiment

FIG. 2 is a block diagram showing an overall configuration of an LTEcommunication system 200 which is under discussion of 3GPP. FIG. 2 isdescribed here. A radio access network is referred to as an evolveduniversal terrestrial radio access network (E-UTRAN) 201. A userequipment device (hereinafter, referred to as a “user equipment (UE)”)202 that is a communication terminal device is capable of radiocommunication with a base station device (hereinafter, referred to as a“base station (E-UTRAN Node B: eNB)”) 203 and transmits and receivessignals through radio communication.

Here, the “communication terminal device” covers not only a userequipment device such as a mobile phone terminal device, but also anunmovable device such as a sensor. In the following description, the“communication terminal device” may be simply referred to as a“communication terminal”.

The E-UTRAN is composed of one or a plurality of base stations 203,provided that a control protocol for the user equipment 202 such as aradio resource control (RRC), and user planes (hereinafter also referredto as “U-planes”) such as a packet data convergence protocol (PDCP),radio link control (RLC), medium access control (MAC), or physical layer(PHY) are terminated in the base station 203.

The control protocol radio resource control (RRC) between the userequipment 202 and the base station 203 performs, for example, broadcast,paging, and RRC connection management. The states of the base station203 and the user equipment 202 in RRC are classified into RRC_IDLE andRRC_CONNECTED.

In RRC_IDLE, public land mobile network (PLMN) selection, systeminformation (SI) broadcast, paging, cell re-selection, mobility, and thelike are performed. In RRC_CONNECTED, the user equipment has RRCconnection and is capable of transmitting and receiving data to and froma network. In RRC_CONNECTED, for example, handover (HO) and measurementof a neighbor cell are performed.

The base stations 203 are classified into eNBs 207 and Home-eNBs 206.The communication system 200 is equipped with an eNB group 203-1including a plurality of eNBs 207 and a Home-eNB group 203-2 including aplurality of Home-eNBs 206. A system, composed of an evolved packet core(EPC) being a core network and an E-UTRAN 201 being a radio accessnetwork, is referred to as an evolved packet system (EPS). The EPC beinga core network and the E-UTRAN 201 being a radio access network may becollectively referred to as a “network”.

The eNB 207 is connected to an MME/S-GW unit (hereinafter, also referredto as an “MME unit”) 204 including a mobility management entity (MME), aserving gateway (S-GW) or an MME and an S-GW by means of an Siinterface, and control information is communicated between the eNB 207and the MME unit 204. A plurality of MME units 204 may be connected toone eNB 207. The eNB s 207 are connected to each other by means of an X2interface, and control information is communicated between the eNBs 207.

The Home-eNB 206 is connected to the MME unit 204 by means of an S1interface, and control information is communicated between the Home-eNB206 and the MME unit 204. A plurality of Home-eNBs 206 are connected toone MME unit 204. Alternatively, the Home-eNB s 206 are connected to theMME units 204 through a Home-eNB gateway (HeNBGW) 205. The Home-eNB 206is connected to the HeNBGW 205 by means of an S1 interface, and theHeNBGW 205 is connected to the MME unit 204 by means of an S1 interface.

One or a plurality of Home-eNBs 206 are connected to one HeNBGW 205, andinformation is communicated therebetween through an S1 interface. TheHeNBGW 205 is connected to one or a plurality of MME units 204, andinformation is communicated therebetween through an S1 interface.

The MME units 204 and HeNBGW 205 are entities of higher layer,specifically, higher nodes, and control the connections between the userequipment (UE) 202 and the eNB 207 and the Home-eNB 206 being basestations. The MME units 204 configure an EPC being a core network. Thebase station 203 and the HeNBGW 205 configure the E-UTRAN 201.

Further, the configuration below is studied in 3GPP. The X2 interfacebetween the Home-eNBs 206 is supported. In other words, the Home-eNBs206 are connected to each other by means of an X2 interface, and controlinformation is communicated between the Home-eNBs 206. The HeNBGW 205appears to the MME unit 204 as the Home-eNB 206. The HeNBGW 205 appearsto the Home-eNB 206 as the MME unit 204.

The interfaces between the Home-eNBs 206 and the MME units 204 are thesame, which are the S1 interfaces, in both cases where the Home-eNB 206is connected to the MME unit 204 through the HeNBGW 205 and it isdirectly connected to the MME unit 204.

The base station device 203 may configure a single cell or a pluralityof cells. Each cell has a range predetermined as a coverage in which thecell can communicate with the user equipment 202 and performs radiocommunication with the user equipment 202 within the coverage. In a casewhere one base station device 203 configures a plurality of cells, everycell is configured so as to communicate with the user equipment 202.

FIG. 3 is a block diagram showing the configuration of the userequipment 202 of FIG. 2 that is a communication terminal according tothe present invention. The transmission process of the user equipment202 shown in FIG. 3 is described. First, a transmission data buffer unit303 stores the control data from a protocol processing unit 301 and theuser data from an application unit 302. The data stored in thetransmission data buffer unit 303 is passed to an encoding unit 304, andis subjected to an encoding process such as error correction. There mayexist the data output from the transmission data buffer unit 303directly to a modulating unit 305 without the encoding process. The dataencoded by the encoding unit 304 is modulated by the modulating unit305. The modulated data is converted into a baseband signal, and thebaseband signal is output to a frequency converting unit 306 and is thenconverted into a radio transmission frequency. After that, atransmission signal is transmitted from an antenna 307 to the basestation 203.

The user equipment 202 executes the reception process as follows. Theradio signal from the base station 203 is received through the antenna307. The received signal is converted from a radio reception frequencyinto a baseband signal by the frequency converting unit 306 and is thendemodulated by a demodulating unit 308. The demodulated data is passedto a decoding unit 309, and is subjected to a decoding process such aserror correction. Among the pieces of decoded data, the control data ispassed to the protocol processing unit 301, and the user data is passedto the application unit 302. A series of processes by the user equipment202 is controlled by a control unit 310. This means that, though notshown in FIG. 3 , the control unit 310 is connected to the individualunits 301 to 309.

FIG. 4 is a block diagram showing the configuration of the base station203 of FIG. 2 that is a base station according to the present invention.The transmission process of the base station 203 shown in FIG. 4 isdescribed. An EPC communication unit 401 performs data transmission andreception between the base station 203 and the EPC (such as the MME unit204), HeNBGW 205, and the like. A communication with another basestation unit 402 performs data transmission and reception to and fromanother base station. The EPC communication unit 401 and thecommunication with another base station unit 402 each transmit andreceive information to and from a protocol processing unit 403. Thecontrol data from the protocol processing unit 403, and the user dataand the control data from the EPC communication unit 401 and thecommunication with another base station unit 402 are stored in atransmission data buffer unit 404.

The data stored in the transmission data buffer unit 404 is passed to anencoding unit 405, and then an encoding process such as error correctionis performed for the data. There may exist the data output from thetransmission data buffer unit 404 directly to a modulating unit 406without the encoding process. The encoded data is modulated by themodulating unit 406. The modulated data is converted into a basebandsignal, and the baseband signal is output to a frequency converting unit407 and is then converted into a radio transmission frequency. Afterthat, a transmission signal is transmitted from an antenna 408 to one ora plurality of user equipments 202.

The reception process of the base station 203 is executed as follows. Aradio signal from one or a plurality of user equipments 202 is receivedthrough the antenna 408. The received signal is converted from a radioreception frequency into a baseband signal by the frequency convertingunit 407, and is then demodulated by a demodulating unit 409. Thedemodulated data is passed to a decoding unit 410 and then subject to adecoding process such as error correction. Among the pieces of decodeddata, the control data is passed to the protocol processing unit 403,the EPC communication unit 401, or the communication with another basestation unit 402, and the user data is passed to the EPC communicationunit 401 and the communication with another base station unit 402. Aseries of processes by the base station 203 is controlled by a controlunit 411. This means that, though not shown in FIG. 4 , the control unit411 is connected to the individual units 401 to 410.

FIG. 5 is a block diagram showing the configuration of the MME accordingto the present invention. FIG. 5 shows the configuration of an MME 204 aincluded in the MME unit 204 shown in FIG. 2 described above. A PDN GWcommunication unit 501 performs data transmission and reception betweenthe MME 204 a and the PDN GW. A base station communication unit 502performs data transmission and reception between the MME 204 a and thebase station 203 by means of the S1 interface. In a case where the datareceived from the PDN GW is user data, the user data is passed from thePDN GW communication unit 501 to the base station communication unit 502via a user plane communication unit 503 and is then transmitted to oneor a plurality of base stations 203. In a case where the data receivedfrom the base station 203 is user data, the user data is passed from thebase station communication unit 502 to the PDN GW communication unit 501via the user plane communication unit 503 and is then transmitted to thePDN GW.

In a case where the data received from the PDN GW is control data, thecontrol data is passed from the PDN GW communication unit 501 to acontrol plane control unit 505. In a case where the data received fromthe base station 203 is control data, the control data is passed fromthe base station communication unit 502 to the control plane controlunit 505.

A HeNBGW communication unit 504 is provided in a case where the HeNBGW205 is provided, which performs data transmission and reception betweenthe MME 204 a and the HeNBGW 205 by means of the interface (IF)according to an information type. The control data received from theHeNBGW communication unit 504 is passed from the HeNBGW communicationunit 504 to the control plane control unit 505. The processing resultsof the control plane control unit 505 are transmitted to the PDN GW viathe PDN GW communication unit 501. The processing results of the controlplane control unit 505 are transmitted to one or a plurality of basestations 203 by means of the S1 interface via the base stationcommunication unit 502, and are transmitted to one or a plurality ofHeNBGWs 205 via the HeNBGW communication unit 504.

The control plane control unit 505 includes a NAS security unit 505-1,an SAE bearer control unit 505-2, and an idle state mobility managingunit 505-3, and performs an overall process for the control plane(hereinafter also referred to as a “C-plane”). The NAS security unit505-1 provides, for example, security of a non-access stratum (NAS)message. The SAE bearer control unit 505-2 manages, for example, asystem architecture evolution (SAE) bearer. The idle state mobilitymanaging unit 505-3 performs, for example, mobility management of anidle state (LTE-IDLE state which is merely referred to as idle as well),generation and control of a paging signal in the idle state, addition,deletion, update, and search of a tracking area of one or a plurality ofuser equipments 202 being served thereby, and tracking area listmanagement.

The MME 204 a distributes a paging signal to one or a plurality of basestations 203. In addition, the MME 204 a performs mobility control of anidle state. When the user equipment is in the idle state and an activestate, the MME 204 a manages a list of tracking areas. The MME 204 abegins a paging protocol by transmitting a paging message to the cellbelonging to a tracking area in which the UE is registered. The idlestate mobility managing unit 505-3 may manage the CSG of the Home-eNBs206 to be connected to the MME 204 a, CSG IDs, and a whitelist.

An example of a cell search method in a mobile communication system isdescribed next. FIG. 6 is a flowchart showing an outline from a cellsearch to an idle state operation performed by a communication terminal(UE) in the LTE communication system. When starting a cell search, inStep ST601, the communication terminal synchronizes slot timing andframe timing by a primary synchronization signal (P-SS) and a secondarysynchronization signal (S-SS) transmitted from a neighbor base station.

The P-SS and S-SS are collectively referred to as a synchronizationsignal (SS). Synchronization codes, which correspond one-to-one to PCIsassigned per cell, are assigned to the synchronization signals (SSs).The number of PCIs is currently studied in 504 ways. The 504 ways ofPCIs are used for synchronization, and the PCIs of the synchronizedcells are detected (specified).

In Step ST602, next, the user equipment detects a cell-specificreference signal (CRS) being a reference signal (RS) transmitted fromthe base station per cell and measures the reference signal receivedpower (RSRP). The codes corresponding one-to-one to the PCIs are usedfor the reference signal RS. Separation from another cell is enabled bycorrelation using the code. The code for RS of the cell is calculatedfrom the PCI specified in Step ST601, so that the RS can be detected andthe RS received power can be measured.

In Step ST603, next, the user equipment selects the cell having the bestRS received quality, for example, the cell having the highest RSreceived power, that is, the best cell, from one or more cells that havebeen detected up to Step ST602.

In Step ST604, next, the user equipment receives the PBCH of the bestcell and obtains the BCCH that is the broadcast information. A masterinformation block (MIB) containing the cell configuration information ismapped to the BCCH over the PBCH. Accordingly, the MIB is obtained byobtaining the BCCH through reception of the PBCH.

Examples of the MIB information include the downlink (DL) systembandwidth (also referred to as a transmission bandwidth configuration(dl-bandwidth)), the number of transmission antennas, and a system framenumber (SFN).

In Step ST605, next, the user equipment receives the DL-SCH of the cellbased on the cell configuration information of the MIB, to therebyobtain a system information block (SIB) 1 of the broadcast informationBCCH. The SIB1 contains the information about the access to the cell,information about cell selection, and scheduling information on anotherSIB (SIBk; k is an integer equal to or greater than two). In addition,the SIB1 contains a tracking area code (TAC).

In Step ST606, next, the communication terminal compares the TAC of theSIB1 received in Step ST605 with the TAC portion of a tracking areaidentity (TAI) in the tracking area list that has already been possessedby the communication terminal. The tracking area list is also referredto as a TAI list. TAI is the identification information for identifyingtracking areas and is composed of a mobile country code (MCC), a mobilenetwork code (MNC), and a tracking area code (TAC). MCC is a countrycode. MNC is a network code. TAC is the code number of a tracking area.

If the result of the comparison of Step ST606 shows that the TACreceived in Step ST605 is identical to the TAC included in the trackingarea list, the user equipment enters an idle state operation in thecell. If the comparison shows that the TAC received in Step ST605 is notincluded in the tracking area list, the communication terminal requiresa core network (EPC) including MME to change a tracking area through thecell for performing tracking area update (TAU).

The device configuring a core network (hereinafter, also referred to asa “core-network-side device”) updates the tracking area list based on anidentification number (such as UE-ID) of a communication terminaltransmitted from the communication terminal together with a TAU requestsignal. The core-network-side device transmits the updated tracking arealist to the communication terminal. The communication terminal rewrites(updates) the TAC list of the communication terminal based on thereceived tracking area list. After that, the communication terminalenters the idle state operation in the cell.

Widespread use of smartphones and tablet terminal devices explosivelyincreases traffic in cellular radio communications, causing a fear ofinsufficient radio resources all over the world. To increase spectralefficiency, thus, it is studied to downsize cells for further spatialseparation.

In the conventional configuration of cells, the cell configured by aneNB has a relatively-wide-range coverage. Conventionally, cells areconfigured such that relatively-wide-range coverages of a plurality ofcells configured by a plurality of macro eNBs cover a certain area.

When cells are downsized, the cell configured by an eNB has anarrow-range coverage compared with the coverage of a cell configured bya conventional eNB. Thus, in order to cover a certain area as in theconventional case, a larger number of downsized eNBs than theconventional eNBs are required.

In the description below, a “macro cell” refers to a cell having arelatively wide coverage, such as a cell configured by a conventionaleNB, and a “macro eNB” refers to an eNB configuring a macro cell. A“small cell” refers to a cell having a relatively narrow coverage, suchas a downsized cell, and a “small eNB” refers to an eNB configuring asmall cell.

The macro eNB may be, for example, a “wide area base station” describedin Non-Patent Document 7.

The small eNB may be, for example, a low power node, local area node, orhotspot. Alternatively, the small eNB may be a pico eNB configuring apico cell, a femto eNB configuring a femto cell, HeNB, remote radio head(RRH), remote radio unit (RRU), remote radio equipment (RRE), or relaynode (RN). Still alternatively, the small eNB may be a “local area basestation” or “home base station” described in Non-Patent Document 7.

FIG. 7 shows the concept of the cell configuration in which macro eNBsand small eNBs coexist. The macro cell configured by a macro eNB has arelatively-wide-range coverage 701. A small cell configured by a smalleNB has a coverage 702 whose range is narrower than that of the coverage701 of a macro eNB (macro cell).

When a plurality of eNBs coexist, the coverage of the cell configured byan eNB may be included in the coverage of the cell configured by anothereNB. In the cell configuration shown in FIG. 7 , as indicated by areference “704” or “705”, the coverage 702 of the small cell configuredby a small eNB may be included in the coverage 701 of the macro cellconfigured by a macro eNB.

As indicated by the reference “705”, the coverages 702 of a pluralityof, for example, two small cells may be included in the coverage 701 ofone macro cell. A user equipment (UE) 703 is included in, for example,the coverage 702 of the small cell and performs communication via thesmall cell.

In the cell configuration shown in FIG. 7 , as indicated by a reference“706”, the coverage 701 of the macro cell configured by a macro eNB mayoverlap the coverages 702 of the small cells configured by small eNB sin a complicated manner.

As indicated by a reference “707”, the coverage 701 of the macro cellconfigured by a macro eNB need not overlap the coverages 702 of thesmall cells configured by small eNBs.

Further, as indicated by a reference “708”, the coverages 702 of a largenumber of small cells configured by a large number of small eNBs may beconfigured in the coverage 701 of one macro cell configured by one macroeNB.

One of the services in NR is Ultra Reliability, Low LatencyCommunication (URLLC) requiring the communication with low latency andhigh reliability. In the 3GPP standardization meeting, supporting thepacket duplication in the PDCP layer has been agreed for satisfying boththe low latency and the high reliability (see Non-Patent Document 11(3GPP R2-1700672)). In NR, the packet duplication is performed using theconfiguration of carrier aggregation (CA) (see Non-Patent Document 9(3GPP TR 38.804 V14.0.0)).

In the packet duplication, associating a logical channel through whicheach of duplicated packets passes with a radio carrier to be used fortransmitting each of the packets, based on the setting with the RRCsignaling has been agreed in the 3GPP meeting (see Non-Patent Document12 (Draft Report of 3GPP TSG RAN WG2 meeting #98, Hangzhou, China, 15-19May, 2017)). Moreover, controlling activation/deactivation of the packetduplication via the MAC signaling has been agreed in the 3GPP meeting(see Non-Patent Document 12).

Including, in the MAC signaling for controlling activation/deactivationof the packet duplication, an identifier of a bearer and a PDCP sequencenumber for activating/deactivating the packet duplication has beenproposed (see Non-Patent Document 13 (3GPP R2-1704578)). Including anidentifier of a logical channel in the MAC signaling has also beenproposed (see Non-Patent Document 14 (3GPP R2-1704660)).

In the conventional LTE, activation/deactivation of an SCell issupported (see Non-Patent Document 15 (3GPP TS36.321 v14.3.0)). A basestation controls the activation/deactivation of the SCell for the UE.The MAC signaling is used for this control. After receiving the MACsignaling, the UE starts or stops transmission and reception using theSCell at a preset timing.

Regarding the packet duplication and the SCell control, preventing thepacket duplication by controlling activation of the packet duplicationduring a deactivated state of the SCell, or performing the packetduplication by activating the SCell has been proposed (see Non-PatentDocument 16 (3GPP R2-1706867)). Deactivating the packet duplicationthrough implicit deactivation of the SCell upon expiration of an SCelldeactivation timer during an activated state of the packet duplication,or continuing the packet duplication with continuation of activation ofthe SCell has also been proposed (see Non-Patent Document 16).

However, none discloses details of contention processes, in a contentionbetween the packet duplication and the SCell control which is describedin Non-Patent Document 16. Moreover, none discloses operations when theMAC signaling for the packet duplication contends with the MAC signalingfor activating/deactivating the SCell. Thus, upon occurrence of thecontention, the UE does not know how to perform the processes for thepacket duplication, and thus may malfunction.

The following problem may occur, when the MAC signaling for controllingthe packet duplication includes a PDCP sequence number and the MACsignaling undelivered from the base station to the UE causes repetitionof the HARQ retransmission. In other words, when the UE starts totransmit a PDCP PDU with the PDCP sequence number during the repeatedHARQ retransmission, the UE does not know how to perform the processesfor the packet duplication after normally receiving the MAC signaling.Thus, the UE may malfunction.

The first embodiment discloses a method for solving such a problem.

Priorities are defined between the packet duplication control and theSCell control. The UE may prioritize the SCell control over the packetduplication control. The SCell control may be the MAC signaling fordeactivating the SCell. For example, the UE which is activating thepacket duplication may deactivate the packet duplication upon receipt ofthe MAC signaling for deactivating the SCell. Consequently, the powerconsumption in the UE and the base station can be reduced.

The deactivation of the packet duplication may be stop of transmissionof duplicated packets in a radio section, cancelation of the associationbetween a logical channel and a transmission carrier, or a combinationof these two. The timings of these two may be identical or different.The same may apply to the following description according to the presentinvention.

According to the present invention, the activation of the packetduplication may be start of transmission of the duplicated packets inthe radio section, start of the association between the logical channeland the transmission carrier, or a combination of these two. The timingsof these two may be identical or different.

The UE may deactivate the packet duplication at the timing to deactivatethe SCell. Consequently, the complexity in the control in the UE can beavoided. Alternatively, the UE may deactivate the packet duplication atthe time of receiving the MAC signaling for deactivating the SCell. Thetime of receiving the MAC signaling may be, for example, immediatelyafter receiving the MAC signaling. The resources can be saved. Anotherexample timing to deactivate the packet duplication may be at thecompletion of transmission of all the PDCP PDUs that are beingtransmitted at the time of receiving the MAC signaling. This can ensurethe reliability in transmitting the PDCP PDUs, and prevent the bufferoccupancy occurring when the RLC in the base station cannot receive allthe PDCP PDUs.

Alternatively, the base station may notify the UE of the timing todeactivate the packet duplication. This enables flexible operations ofthe packet duplication. The notification may be included in the MACsignaling for deactivating the SCell. The L1/L2 signaling may be used.

The aforementioned method differs from Non-Patent Document 16 (3GPPR2-1706867) in not implicit deactivation of the SCell but explicitdeactivation of the SCell using the MAC signaling.

The deactivation timing may be indicated by a PDCP sequence number. Thiscan prevent the buffer occupancy occurring when the RLC in the basestation cannot receive all the PDCP PDUs. Alternatively, thedeactivation timing may be a physical timing. Direct control over radioresources can prevent transmission and reception of an unnecessary radiosignal. The physical timing may be indicated by, for example, a physicalframe number, a subframe number, a slot number, a mini-slot number, oranother information representing a timing. Alternatively, the physicaltiming may be a time up to the deactivation timing. The base station andthe UE can appropriately perform processes for deactivating the packetduplication.

The UE may retain an activation/deactivation state of the packetduplication. The UE may retain the state using, for example, a flag forcontrolling the packet duplication. The state may be retained upondeactivation of the SCell. The UE may activate or deactivate the packetduplication in the retained state. The UE may activate or deactivate thepacket duplication, for example, upon activation of the SCell. Forexample, the UE, which has deactivated the SCell during an activatedstate of the packet duplication, may resume the activation of the packetduplication upon receiving again the MAC signaling for activating theSCell. This enables, for example, reduction in the amount of the MACsignaling because the MAC signaling to be used foractivating/deactivating the packet duplication upon activation of theSCell can be unnecessary.

An initial value may be assigned to the activation/deactivation state ofthe packet duplication. The initial value may be defined in a standard,or notified from the base station to the UE. The notification may begiven via the RRC signaling, for example, the RRC-dedicated signaling.

The UE may determine the PDCP SN in resuming the packet duplication toresume the activation of the packet duplication. For example, afterresuming the SCell, the UE may resume the activation of the packetduplication from the PDCP PDU that can be transmitted the earliest. Thisfacilitates the packet duplication control in the UE. Alternatively, thebase station may notify the UE of the timing to resume the packetduplication. The notification may include an identifier of a logicalchannel or a PDCP sequence number. The notification may be informationindicating a physical timing. The notification may be included in theMAC signaling for starting (resuming) of the activation of the SCell tobe transmitted from the base station to the UE.

The UE may update the activation/deactivation state of the packetduplication. The UE may update the state using the MAC signaling foractivating or deactivating the packet duplication. The UE may performthe update in an activated state of the SCell or in a deactivated stateof the SCell. This can disperse the MAC signaling for theactivation/deactivation of the SCell and the packet duplication.Alternatively, the UE need not update the activation/deactivation stateof the packet duplication during a deactivated state of the SCell.Consequently, the complexity in the packet duplication control in thebase station and the UE can be avoided.

The UE need not retain the activation/deactivation state of the packetduplication. The memory usage in the UE can be reduced. The UE maydeactivate the packet duplication upon start or resumption of theactivation of the SCell. The usage of radio resources can be reduced.Alternatively, the UE may activate the packet duplication upon start orresumption of the activation of the SCell. The reliability ofcommunication upon activation of the SCell can be ensured.

The activation/deactivation state of the packet duplication may be setper bearer. This enables flexible operations of the packet duplication.

The UE may prioritize the packet duplication control over the SCellcontrol. The MAC signaling for deactivating the SCell may be used forthe SCell control. For example, the UE which is activating the packetduplication may continue the packet duplication even upon receipt of theMAC signaling for deactivating the SCell. Consequently, the reliabilityin the packet duplication by the UE can be enhanced.

The UE may notify the base station that the deactivation of the SCell isdisabled. The UE may give the notification via the MAC signaling or theL1/L2 signaling. The notification may include a cause for beingdisabled. The cause may be, for example, “during an activated state ofthe packet duplication”. The UE may notify an identifier of a logicalchannel during an activated state of the packet duplication as well. TheUE may notify an identifier of a bearer during an activated state of thepacket duplication. Consequently, the base station can perform a smoothcontrol after the deactivation of the SCell is disabled.

The priorities of the packet duplication control and the SCell controlmay be determined using a packet to be duplicated. The UE may determinewhether to deactivate the SCell using information on the packet to beduplicated. This enables flexible control based on the packet to beduplicated.

As an example determination on the priorities using the packet to beduplicated, the priorities may be determined according to aclassification of, for example, SRBs or DRBs. For example, the packetduplication may be prioritized for the SRBs, whereas the SCell controlmay be prioritized for the DRBs. This enables flexible control dependingon a type of bearer.

Alternatively, the priorities may be determined for each bearer. Forexample, the packet duplication may be prioritized for the SRB0 and theSRB1, whereas the SCell control may be prioritized for the SRB2, theSRB3, and the DRBs. For example, regarding the DRB s, the packetduplication may be prioritized for a DRB, whereas the SCell control maybe prioritized for other DRBs. This enables more flexible control foreach bearer.

The priorities may be determined in a standard, or notified in advancefrom the base station to the UE via the RRC signaling. The prioritiesmay be notified via the MAC signaling. This enables flexible control.

The UE may notify the base station that the deactivation of the SCell isdisabled. The UE may give the notification when a packet for which thepacket duplication is prioritized is used, for example, when a bearerfor which the packet duplication is prioritized uses the SCell. Thenotification method and information included in the notification may beidentical to those previously described. Consequently, the base stationcan perform a smooth control after the deactivation of the SCell isdisabled.

The priorities between the packet duplication control and the SCellcontrol may be applied when a plurality of packets are communicatedusing the SCell. The plurality of packets may be, for example, acombination of packets for which the packet duplication is prioritizedand packets for which the SCell control is prioritized.

In the aforementioned description, the packet duplication may beprioritized. For example, during an activated state of the packetduplication of the plurality of packets, the MAC signaling fordeactivating the SCell may be disabled. In other words, the packetduplication may be continued. This can ensure the reliability in thepacket for which the packet duplication is prioritized. The UE maynotify the base station that the deactivation of the SCell is disabled.The notification method and information included in the notification maybe identical to those previously described. Consequently, the basestation can perform a smooth control after the deactivation of the SCellis disabled.

The UE and the base station may deactivate the packet duplication in apart of packets. The part of packets may be, for example, packets forwhich the SCell control is prioritized. The UE and the base station maycontinue the packet duplication of a packet for which the packetduplication is prioritized. This facilitates the control over the SCellin the base station.

Alternatively, the UE and the base station need not deactivate thepacket duplication in the part of packets. This can ensure thereliability in the communication of the packets.

The UE and the base station may deactivate the SCell when deactivatingthe packet duplication of the packet for which the packet duplication isprioritized. The power consumption can be reduced. The UE may notify thebase station that the deactivation of the SCell is enabled. Thenotification may include a cause for being enabled. The cause may be,for example, the deactivation of the packet duplication of the packetfor which the packet duplication is prioritized. The notification mayinclude information on the packet, for example, an identifier of abearer.

Alternatively, the UE and the base station need not deactivate the SCelleven when deactivating the packet duplication of the packet for whichthe packet duplication is prioritized. This facilitates the control overthe SCell.

The SCell control may be prioritized as another example of theassignment of the priorities between the packet duplication control andthe SCell control when a plurality of packets are communicated. Forexample, during an activated state of the packet duplication of theplurality of packets, the MAC signaling for deactivating the SCell maybe enabled. In other words, the SCell may be deactivated. The powerconsumption can be reduced.

The control of activating the packet duplication may be prioritized overa deactivated state of the SCell as an example assignment of thepriorities between the packet duplication control and the SCell control.In other words, the UE may activate the packet duplication. Theactivation of the SCell should be started. The MAC signaling may be usedfor controlling activation of the packet duplication. This can ensurethe reliability.

Alternatively, the deactivated state of the SCell may be prioritizedover the control of activating the packet duplication. In other words,the UE may maintain the deactivation of the SCell.

The UE may notify the base station that the packet duplication isdisabled. The UE may give the notification during or upon deactivationof the SCell. The UE may give the notification via the MAC signaling orthe L1/L2 signaling. The notification may include a target logicalchannel identifier. The notification may include the cause why thepacket duplication is disabled. The cause may be, for example, “during adeactivated state of the SCell”. This enables the base station toappropriately and promptly control the packet duplication.

The UE whose control of activating the packet duplication is disabledmay activate the packet duplication using the control for activating theSCell. The control for activating the SCell may be the MAC signaling forinstructing activation of the SCell. When the UE activates the packetduplication, the UE may use the activation/deactivation state of thepacket duplication. For example, the UE may set the state to“activation” using the control of activating the packet duplication, forexample, using the MAC signaling for activating the packet duplication.

The control of deactivating the packet duplication may be prioritizedover an activated state of the SCell as another example assignment ofthe priorities between the packet duplication control and the SCellcontrol. In other words, the UE may deactivate the SCell using the MACsignaling for deactivating the packet duplication. The UE may deactivatethe SCell when there is no other bearer for the UE to communicate withthe base station using the SCell. This can reduce the power consumptionof the UE.

The base station may include, in the MAC signaling for controlling theactivation/deactivation of the packet duplication, informationindicating the activation/deactivation timing of the packet duplication.The timing may be a physical timing. Direct control of radio resourcescan prevent transmission and reception of an unnecessary radio signal.The physical timing may be indicated by, for example, a physical framenumber, a subframe number, a slot number, a mini-slot number, or anotherinformation representing a timing. Alternatively, the physical timingmay be a time up to the activation/deactivation timing. The base stationand the UE can appropriately perform processes for deactivating thepacket duplication.

The UE may activate/deactivate the packet duplication at theactivation/deactivation timing. Alternatively, the UE mayactivate/deactivate the packet duplication from a PDCP PDU boundary thatis the earliest since the activation/deactivation timing. This canprevent discontinuous transmission operations of the UE due to theactivation/deactivation of the packet duplication. This can also preventthe buffer occupancy occurring when the RLC in the base station cannotreceive all the PDCP PDUs.

Another information indicating the activation/deactivation timing may bea PDCP sequence number. This can prevent the buffer occupancy occurringwhen the RLC in the base station cannot receive all the PDCP PDUs.

The base station need not include, in the MAC signaling for controllingthe activation/deactivation of the packet duplication, informationindicating the activation/deactivation timing of the packet duplication.The UE may activate/deactivate the packet duplication immediately afterreceiving the MAC signaling. For example, the UE may activate/deactivatethe packet duplication from the timing (e.g., subframe, slot, mini-slot,or TTI) immediately after receiving the MAC signaling. The timing toactivate/deactivate the packet duplication may be the next schedulingtiming after the UE returns Ack in response to the MAC signaling.Alternatively, the timing to activate/deactivate the packet duplicationmay be the PDCP PDU boundary that is the earliest since the receptiontiming of the MAC signaling in the UE. Alternatively, the UE mayactivate/deactivate the packet duplication after a lapse of apredetermined duration since receipt of the MAC signaling. Thepredetermined duration may be predefined in a standard, or broadcastfrom the base station to the UE. The predetermined duration may benotified dedicatedly from the base station to the UE. The dedicatednotification may be given via the RRC signaling. This enables reductionin the amount of signaling required at the activation/deactivationtiming of the packet duplication.

The base station may include, in the MAC signaling for controlling theactivation/deactivation of the packet duplication, information forcontrolling the activation/deactivation of an SCell to be used for thepacket duplication. The UE may activate/deactivate the SCell using theinformation. This enables the base station to flexibly control the SCellwith the packet duplication control.

Conversely, the base station may include, in the MAC signaling forcontrolling the activation/deactivation of the SCell, information forcontrolling the activation/deactivation of the packet duplication forcommunication using the SCell. The UE may activate/deactivate the packetduplication using the information. This enables the base station toflexibly control the SCell with the packet duplication control.

Alternatively, the MAC signaling for controlling theactivation/deactivation of the packet duplication and the MAC signalingfor controlling the activation/deactivation of the SCell may beintegrated into one MAC signaling. The one MAC signaling may be set as anew MAC signaling.

Alternatively, the base station may simultaneously transmit the MACsignaling for controlling the activation/deactivation of the packetduplication and the MAC signaling for controlling theactivation/deactivation of the SCell. Both the MAC signalings may betransmitted in the same transport block or different transport blocks.As an example of the transmission in the different transport blocks, theMAC signalings may be transmitted in different carriers. This canexpedite the control over both of the SCell and the packet duplication.Alternatively, the MAC signaling for controlling theactivation/deactivation of the packet duplication and the MAC signalingfor controlling the activation/deactivation of the SCell may beintegrated. This can reduce the amount of signaling.

The control of activating the packet duplication may be prioritized overthe control of activating the SCell as another example assignment of thepriorities between the packet duplication control and the SCell control.For example, the UE may activate the SCell at the timing to activate thepacket duplication. The UE may activate the packet duplication.Consequently, the reliability for transmitting a packet from the UE tothe base station can be enhanced.

Alternatively, the control of activating the SCell may be prioritizedover the control of activating the packet duplication. For example, theUE may activate the packet duplication at the timing to activate theSCell. Consequently, the complexity in the SCell control in the basestation and the UE can be avoided.

The UE may notify the base station that activation of the SCell isdisabled. The UE may give the notification, for example, when the SCellcannot be activated. The notification may include a cause for beingdisabled. The cause may be, for example, a fault in a transceiver forcarrier frequency of the SCell, or the shortage of resources for theSCell. In response to the notification, the base station may control theactivation/deactivation of the other SCells. Consequently, the basestation can perform a smooth control after the activation of the SCellis disabled.

The control of activating the packet duplication may be prioritized overthe control of deactivating the SCell as another example assignment ofthe priorities between the packet duplication control and the SCellcontrol. For example, the UE may activate the packet duplication. Inother words, the control of deactivating the SCell may be disabled. Theoperation may be performed, for example, when the SCell operates and thepacket duplication is deactivated. This can enhance the reliability fortransmitting a packet. The UE may notify the base station that thedeactivation of the SCell is disabled. In response to the notification,the base station can appropriately control the radio resources.

Alternatively, the control of deactivating the SCell may be prioritizedover the control of activating the packet duplication. For example, theUE may deactivate the SCell. In other words, the control of activatingthe packet duplication may be disabled. The radio resources can besaved. The UE may notify the base station that the packet duplication isdisabled. In response to the notification, the base station canappropriately determine the radio resources to be used for transmissionand reception with the UE.

The control of deactivating the packet duplication may be prioritizedover the control of deactivating the SCell as another example assignmentof the priorities between the packet duplication control and the SCellcontrol. For example, the UE may deactivate the packet duplication atthe timing to deactivate the packet duplication. For example, when thetiming to deactivate the SCell precedes the timing to deactivate thepacket duplication that is indicated by the MAC signaling fordeactivating the packet duplication, the UE may wait deactivation of theSCell until the timing to deactivate the packet duplication. This canensure the reliability for transmitting a packet.

Alternatively, the control of deactivating the SCell may be prioritizedover the control of deactivating the packet duplication. For example,the UE may deactivate the packet duplication at the timing to deactivatethe SCell. For example, when the timing to deactivate the SCell precedesthe timing to deactivate the packet duplication that is indicated by theMAC signaling for deactivating the packet duplication, the UE maydeactivate the packet duplication simultaneously with the timing todeactivate the activated SCell. This can ensure the reliability fortransmitting a packet.

The UE may determine activation of the packet duplication and activationof the SCell, using the MAC signaling for activating/deactivating thepacket duplication and the MAC signaling for activating/deactivating theSCell. For example, the UE may determine to activate the packetduplication, using the MAC signaling for activating the packetduplication or using both of the MAC signaling for activating the packetduplication and the MAC signaling for activating the SCell. Thedetermination using both of the MAC signalings may be obtained by an OR,an AND, or another logical operation of the MAC signalings.Alternatively, for example, the UE may determine to activate the SCell,using the MAC signaling for activating the SCell or using both of theMAC signaling for activating the packet duplication and the MACsignaling for activating the SCell. The determination using both of theMAC signalings may be obtained by an OR, an AND, or another logicaloperation of the MAC signalings. This enables flexible control over thepacket duplication and the activation of the SCell.

A flag on the packet duplication and a flag on the activation of theSCell may replace the MAC signaling for activating/deactivating thepacket duplication and the MAC signaling for activating/deactivating theSCell. The flag on the packet duplication may be, for example, a flagretaining the activation/deactivation state of the packet duplication.The flag on the activation of the SCell may, for example, switch itsvalue between the activation and the deactivation according to the MACsignaling for activating/deactivating the SCell. This enables flexibleand easy control over the packet duplication and the activation of theSCell.

The UE may duplicate the PDCP PDU in a PDCP layer, regardless of whetherthe packet duplication is activated/deactivated. The PDCP layer of theUE may transfer the duplicated PDCP PDUs to the RLC layer. The RLC layermay transfer the PDCP PDUs to the MAC layer. The UE may perform theduplicating and/or transferring process using the RRC signaling from thebase station. The RRC signaling may be a signaling for associating alogical channel through which each packet to be duplicated passes with aradio carrier to be used for transmitting each packet. The UE maydeactivate the duplication and/or transferring, using the RRC signalingfrom the base station. The RRC signaling may be a signaling forcanceling the association between the logical channel through which eachpacket to be duplicated passes and the radio carrier to be used fortransmitting each packet. This enables, for example, the UE to expeditea process of transmitting duplicated packets upon activation of thepacket duplication.

The UE may activate/deactivate the packet duplication at the timing ofaccurately receiving the MAC signaling for controllingactivation/deactivation of the packet duplication. The timing ofaccurately receiving the MAC signaling may be after the timing toactivate/deactivate the packet duplication instructed via the MACsignaling. The timing after the timing to activate/deactivate the packetduplication instructed via the MAC signaling may be, for example, thetiming when the HARQ retransmission is performed. The timing may be, forexample, specified by a PDCP sequence number or a physical timing. Thephysical timing may be indicated by, for example, a physical framenumber, a subframe number, a slot number, or a mini-slot number.

The base station may transmit the MAC signaling to the UE in advance,using a plurality of HARQ processes. All the HARQ processes may be used.This can enhance the reliability in transmission and reception via theMAC signaling.

The base station may stop transmission of the MAC signaling to the UE.The base station may stop transmission of the MAC signaling, forexample, upon receipt of Ack from the UE in response to the MACsignaling using the other HARQ processes. This can save the radioresources.

The UE may activate/deactivate the packet duplication using the MACsignaling initially received. The MAC signaling initially received maybe, for example, the MAC signaling which the UE has initially receivedamong the MAC signalings transmitted via a plurality of HARQ processes.The UE may ignore or discard the MAC signalings received for the secondtime and after. This enables the UE to perform a prompt process.

Alternatively, the UE may activate the packet duplication retroactively.The UE may activate the packet duplication by tracing back to the timingto activate the packet duplication instructed via the MAC signaling. TheUE may activate the packet duplication using data stored in a buffer ofthe L2 layer, for example, a buffer of the PDCP layer. This can ensurethe reliability of the packet duplication.

Alternatively, the UE may duplicate the packet of data as far astraceable. The UE may perform the operation, for example, when no dataup to the timing to activate the packet duplication instructed via theMAC signaling remains. The UE may perform the operation described abovewhen the data up to the timing to activate the packet duplicationinstructed via the MAC signaling remains. This can ensure thereliability of the packet duplication.

Alternatively, the UE may activate/deactivate the packet duplication atthe timing to activate/deactivate the packet duplication instructed viathe MAC signaling. The timing to activate/deactivate the packetduplication may be, for example, the timing to activate/deactivate thepacket duplication after cycling through all the numbers. For example,upon receiving, from the base station, the MAC signaling for activatingthe packet duplication from the PDCP PDU sequence number 5 duringexecution of the process of transmitting the PDCP PDU with the PDCP PDUsequence number 7, the UE may activate the packet duplication from thePDCP PDU with the next PDCP PDU sequence number 5 after cycling throughall the PDCP PDU sequence numbers. Consequently, the complexity ofdesign in the UE can be avoided.

FIG. 8 is a sequence diagram illustrating operations when the UEreceives the MAC signaling for activating the packet duplication after aspecified timing due to occurrence of the HARQ retransmission. AlthoughFIG. 8 illustrates the sequence for activating the packet duplication,it may be applied to deactivation of the packet duplication. Althoughthe PDCP sequence number is used as the specified timing in FIG. 8 , aphysical timing may be used. The physical timing may be the onepreviously described.

In Step ST801 of FIG. 8 , the base station determines to activate thepacket duplication. In Step ST802, the base station notifies the UE ofthe MAC signaling for activating the packet duplication. The signalingincludes an uplink PDCP sequence number n for activating the packetduplication in the UE. In FIG. 8 , the UE cannot accurately receive theMAC signaling for activating the packet duplication in Step ST802, andnotifies the base station of Nack in Step ST803. Upon receipt of theNack in Step ST803, the base station retransmits the MAC signaling ofStep ST802 to the UE in Step ST804. In FIG. 8 , the UE cannot accuratelyreceive the MAC signaling for activating the packet duplication in StepST804, and notifies the base station of Nack again in Step ST805.

In Step ST806 of FIG.8, the sequence number of the PDCP PDU at which theUE performs a transmission process reaches n. The UE transmits the PDCPPDU with the sequence number n to the base station without the packetduplication.

In Step ST807 of FIG. 8 , the base station performs the secondretransmission of the MAC signaling to the UE. In Step ST808, the UEnotifies the base station of Ack in response to Step ST807.

In FIG. 8 , the UE, which can accurately receive the MAC signaling foractivating the packet duplication in Step ST807, activates the packetduplication in Step ST809. In Steps ST810 and ST811, the UE transmitsthe original packet and the duplicated packet to the base station. InStep ST812, the base station detects identical packets, and removes oneof the packets.

The base station may set the RLC layer for duplicated packets. The basestation may make the setting immediately after determining to activatethe packet duplication. The base station can promptly activate thepacket duplication even when the time until the specified timing isshort.

The base station may make the setting of the RLC layer for duplicatedpackets after receiving Ack from the UE in response to the MAC signalingfor notifying the UE to activate the packet duplication. This canminimize the time to allocate memory with the RLC setting as necessary.

The PDCP layer of the base station may instruct the RLC layer toinitialize the RLC layer. The RLC layer may initialize the RLC inresponse to the instruction. The PDCP layer may issue the instructionafter finishing receiving the PDCP PDUs up to the PDCP sequence numberindicating the timing to deactivate the packet duplication. Theinstruction may include, for example, an identifier of an RLC entity tobe initialized, or an identifier of a logical channel that uses the RLCentity. The initialization may be, for example, initialization of abuffer in the RLC PDU, initialization of a variable to be used in theRLC entity which is described in 7.1 of Non-Patent Document 17 (TS36.322v14.0.0), or a combination of these two. This enables the PDCP layer ofthe CU to reliably receive the PDCP PDUs up to the PDCP sequence numberindicating the timing.

The method described in the first embodiment may be applied to thepacket duplication using only the SCell. This extends the flexibility inselecting a carrier in the packet duplication. The method described inthe first embodiment may be applied to both the C-Plane and the U-Plane.The malfunctions in the packet duplication can be prevented in both theC-Plane and the U-Plane.

According to the first embodiment, the base station may change a carrierassociated with a logical channel in the packet duplication by the UE.In other words, the base station may change a carrier to be used fortransmitting a logical channel in the packet duplication by the UE. Forexample, the MAC layer of the base station may make this change. Thetolerance to fluctuation in the radio environment during an activatedstate of the packet duplication can be increased.

The base station may notify the UE of changing the carrier to be usedfor transmitting the logical channel. The notification may includecombined information of a logical channel and a carrier being used. Thebase station may give the UE the notification via the MAC signaling.This enables a prompt notification with higher reliability under theHARQ control. Alternatively, the base station may give the UE thenotification via the L1/L2 signaling. This enables a further promptnotification. Alternatively, the base station may give the UE thenotification via the RRC signaling. Consequently, the complexity indesigning a communication system can be avoided.

The UE may enable a signaling for associating a logical channel with atransmission carrier and/or for changing the association which is to betransmitted from the base station. The signaling may be the RRCsignaling, the MAC signaling, or the L1/L2 signaling. The UE may enablethe signaling when the signaling includes an SCell that is not found inan SCell list to be used by the UE. An SCell that is included in theSCell list may be, for example, an SCell included in an SCelladdition/modification list in the signaling for the RRC connectionreconfiguration.

The UE may add, to the SCell list, the SCell that is not found in theSCell list.

The UE may notify the base station of information on the SCell. Theinformation on the SCell may be, for example, a physical cell ID (PCI)of the SCell, an SCell identifier, for example, SCelllndex, or combinedinformation of these. The UE may assign the SCell identifier to theSCell. The SCell identifier may be identical to an SCell identifierassigned by the base station, or a temporary SCell identifier. Thetemporary SCell identifier may be defined in a standard, or broadcast ordedicatedly notified from the base station to the UE in advance. Thebase station may add the Cell to the SCell list to be used by the UE.The base station may notify the UE of information on the added SCell.The information on the added SCell may include an SCell identifier, PCIof the SCell, or both of these. The UE may replace the SCell identifierassigned by its own UE with the SCell identifier notified from the basestation.

The UE may use the RRC signaling to notify information on the SCell tothe base station. For example, when the signaling for associating alogical channel with a transmission carrier which is to be transmittedfrom the base station is the RRC signaling, the UE may give theinformation via the RRC signaling. Sending the signaling and thenotification via the same type of signaling facilitates the process forthe SCell control in the base station.

Alternatively, the UE may notify the information on the SCell to thebase station via the MAC signaling. For example, when the signaling forassociating a logical channel with a transmission carrier which is to betransmitted from the base station is the MAC signaling, the UE maynotify the information via the MAC signaling. In addition to obtainmentof the same advantages as described above, a prompt notification ispossible.

Alternatively, the UE may notify the information on the SCell to thebase station via the L1/L2 signaling. For example, when the signalingfor associating a logical channel with a transmission carrier which isto be transmitted from the base station is the L1/L2 signaling, the UEmay notify the information via the L1/L2 signaling. This enables afurther prompt notification.

The UE may disable the signaling for associating a logical channel witha transmission carrier and/or for changing the association which is tobe transmitted from the base station. The signaling may be identical tothat described above. The UE may disable the signaling when thesignaling includes the SCell that is not found in the SCell list to beused by the UE. The SCell that is not found in the SCell list may beidentical to that described above.

The UE may duplicate the packet with the original setting of the packetduplication. Alternatively, the UE may deactivate the packetduplication. The target packets whose packet duplication is to bedeactivated may include all the packets that the UE duplicates and apacket corresponding to the signaling. Alternatively, the UE may deletethe setting of the packet duplication of the packet corresponding to thesignaling.

The UE may notify the base station that the signaling is disabled. Thenotification may include the cause why the signaling is disabled. Thecause may be, for example, non-existence of the SCell notified via thesignaling in the SCell list to be used by the UE. The signaling mayinclude the information on the SCell. The information on the SCell maybe, for example, information on the SCell that does not exist in theSCell list to be used by the UE, e.g., the PCI of the SCell. Thisfacilitates the control over the SCell in the base station.

The UE may give the notification via the RRC signaling. For example,when the signaling for associating a logical channel with a transmissioncarrier which is to be transmitted from the base station is the RRCsignaling, the UE may give the notification via the RRC signaling.Sending the signaling and the notification via the same type ofsignaling facilitates the process for the SCell control in the basestation.

Alternatively, the UE may give the notification via the MAC signaling.For example, when the signaling for associating a logical channel with atransmission carrier which is to be transmitted from the base station isthe MAC signaling, the UE may notify the information via the MACsignaling. In addition to obtainment of the same advantages as describedabove, a prompt notification is possible.

Alternatively, the UE may give the notification via the L1/L2 signaling.For example, when the signaling for associating a logical channel with atransmission carrier which is to be transmitted from the base station isthe L1/L2 signaling, the UE may notify the information via the L1/L2signaling. This enables a further prompt notification.

The base station may transmit, to the UE, a signaling for adding theSCell to an SCell list for UE use. The base station may transmit, to theUE, a signaling for associating a logical channel with a transmissioncarrier. These enables the packet duplication using the SCell. The basestation may transmit, to the UE, these signalings simultaneously or atdifferent timings. The signalings may be integrated into one signaling.

The first embodiment can prevent malfunctions in the UE upon occurrenceof a contention between the packet duplication and the SCell control.The first embodiment can also prevent the malfunctions in the UE whichoccur when the timing at which the UE receives the MAC signaling foractivating/deactivating the packet duplication from the base station isafter the timing instructed via the MAC signaling.

The First Modification of the First Embodiment

The packet duplication with the CA may be applied to a base station inNR (gNB) which is split into two units.

In 3GPP, splitting the base station in NR (may be hereinafter referredto as a gNB) into two units has been proposed (see Non-Patent Document7). The two units are referred to as the central unit (CU) and thedistributed unit (DU). Regarding sharing functions between the CU andthe DU in the CU-DU split, the CU has the PDCP, and the

DU has the RLC, the MAC, and the PHY (see Non-Patent Document 18 (3GPPR3-171412)).

FIG. 9 illustrates a protocol configuration in the packet duplicationwith the CA to be performed between the gNB with the CU-DU split and theUE.

A New AS layer 1022 in a UE 1014 receives a packet from an upper layer,for example, an application or the RRC to generate a PDCP-SDU andtransmit the PDCP-SDU to a PDCP 1021.

The PDCP 1021 generates a PDCP PDU using the PDCP-SDU, duplicates thePDCP PDU, and transmits the PDCP PDUs to RLCs 1019 and 1020. Each of theRLCs 1019 and 1020 generates an RLC PDU using a corresponding one of thePDCP PDUs, and transmits the RLC PDU to an MAC 1016.

The MAC 1016 generates transport channel data using the RLC PDU receivedfrom the RLC 1019, and transmits the transport channel data to a HARQ1015 for a cell #1. The MAC 1016 generates transport channel data usingthe RLC PDU received from the RLC 1020, and transmits the transportchannel data to a HARQ 1018 for a cell #2.

The HARQ 1015 transmits, to a PHY 1014, the transport channel datagenerated using the RLC PDU from the RLC 1019. The PHY 1014 performsprocesses of coding and modulating the transport channel data, andtransmits the resulting data to a DU 1006 using the cell #1 as a radiosignal. The HARQ 1018 transmits, to a PHY 1017, the transport channeldata generated using the RLC PDU from the RLC 1020. The PHY 1017performs the processes of coding and modulating the transport channeldata, and transmits the resulting data to the DU 1006 using the cell #2as a radio signal.

A PHY 1011 in the DU 1006 receives the signal of the cell #1, performsprocesses of demodulating and decoding the signal, and transmits theresulting signal to a HARQ 1010 as the transport channel data. The HARQ1010 transfers the transport channel data to an MAC 1009. A PHY 1013receives the signal of the cell #2, performs the processes ofdemodulating and decoding the signal, and transmits the resulting signalto a HARQ 1012 as the transport channel data. The HARQ 1012 transfersthe transport channel data to the MAC 1009.

The MAC 1009 generates the RLC PDU using the transport channel data fromeach of the HARQs 1010 and 1012, and transfers the RLC PDU to acorresponding one of the RLCs 1007 and 1008. The RLC 1007 generates thePDCP PDU using the RLC PDU, and transfers the PDCP PDU to a PDCP 1003 ofa CU 1001 through a CU-DU interface 1004. The RLC 1008 generates thePDCP PDU using the RLC PDU, and transfers the PDCP PDU to the PDCP 1003of the CU 1001 through the CU-DU interface 1004.

The PDCP 1003 in the CU 1001 detects redundancy in the PDCP PDUs fromthe RLCs 1007 and 1008, and removes the redundant PDCP PDU. The PDCP1003 generates the PDCP-SDU using the original PDCP PDU, that is, thePDCP PDU that is not removed, and transfers the PDCP-SDU to a New ASlayer 1002.

However, it is not clear which of the CU or the DU determines toduplicate the packet in the gNB with the CU-DU split. A signal betweenthe CU and the DU in the packet duplication is not defined. Thus, the UEhas a problem of failing to duplicate the packet in the communicationwith the gNB with the CU-DU split.

The first modification of the first embodiment solves the problem.

The DU determines to activate the packet duplication. The MAC layer maymake the determination.

The DU may determine to activate the packet duplication, using ameasurement result of an uplink signal. For example, the SRS or an errorrate of the uplink signal such as a BER or a BLER may be used as theuplink signal. Alternatively, the DU may determine to activate thepacket duplication, using the size of uplink transmission data. Forexample, an uplink grant to be transmitted from the DU to the UE, or aBuffer Status Report (BSR) to be received from the UE may be used as thesize of uplink transmission data. Alternatively, the DU may determine toactivate the packet duplication, using a load of each cell. For example,a scheduling state for another UE may be used as a load of each cell.This enables optimization of communication in the whole system.

Non-Patent Document 19 (see R2-1706716) discloses use of the measurementresult of the uplink signal, the size of uplink transmission data, andthe load of each cell. However, the present invention differs fromNon-Patent Document 19 in disclosing specific examples of themeasurement result of the uplink signal, the size of uplink signal data,and the load of each cell.

The DU may transmit, to the CU, a notification indicating activation ofthe packet duplication. The CU may transmit, to the DU, a response tothe notification. The response may include information on the timing toactivate the packet duplication. The information on the timing toactivate the packet duplication may be a PDCP sequence number orinformation on a physical timing similarly to the first embodiment. ThePDCP sequence number may be information on the sequence numbers of thePDCP PDUs received in the PDCP layer of the CU, for example, the largestsequence number of the PDCP PDUs. Information on the PDCP sequencenumbers from the CU can be promptly notified. Alternatively, the CU maynotify the DU of the PDCP sequence number at which the UE activates thepacket duplication. This can reduce the amount of processing in the DU.

The DU may notify the UE of the MAC signaling for activating the packetduplication. The MAC signaling may include information on the timing toactivate the packet duplication similarly to the first embodiment.

The response from the CU to the DU need not include information on thetiming to activate the packet duplication. The MAC signaling from the DUto the UE need not include information on the timing.

The processing in the UE may be identical to that in the firstembodiment. The complexity in the packet duplication which the UEperforms for the base station can be avoided.

The DU need not transmit, to the CU, a notification indicatingactivation of the packet duplication. The CU need not transmit, to theDU, a response to the notification indicating activation of the packetduplication. This can reduce the amount of signaling between the CU andthe DU.

FIG. 10 is a sequence diagram of the packet duplication when the DUdetermines to activate the packet duplication. FIG. 10 illustrates anexample using the PDCP sequence number n as the timing to activate thepacket duplication.

In Step ST1101 of FIG. 10 , the DU determines to activate the packetduplication. In Step ST1102, the DU notifies the CU of activation of thepacket duplication. In Step ST1103, the CU notifies the DU ofacknowledgement of activating the packet duplication. In Step ST1103,the CU may notify information on the timing to activate the packetduplication. In the example of FIG. 10 , the CU notifies the DU of thePDCP sequence number n as the information.

In FIG. 10 , the DU need not notify the CU of Step ST1102. Step ST1103need not include the information on the timing to activate the packetduplication. Alternatively, the CU need not notify the DU of StepST1103. This can reduce the amount of signaling in the interface betweenthe CU and the DU.

In Step ST1104 of FIG. 10 , the DU notifies the UE of the MAC signalingfor activating the packet duplication. In Step ST1104, the DU may notifythe information on the timing to activate the packet duplication. In theexample of FIG. 10 , the DU notifies the UE of the PDCP sequence numbern as the information. In Step ST1105, the UE notifies the DU of Ack inresponse to Step ST1104.

In Step ST1106 of FIG. 10 , the UE activates the packet duplication. InSteps ST1107 and ST1108, the UE transmits the original packet and theduplicated packet to the DU. In Steps ST1109 and ST1110, the DUtransmits the PDCP PDUs received in the Step ST1107 and Step ST1108,respectively, to the CU. In Step ST1111, the CU detects identicalpackets, and removes one of the packets.

In the first modification of the first embodiment, the CU may determineto activate the packet duplication. The RRC layer or the PDCP layer maymake the determination.

The DU may notify the CU of information necessary for determining toactivate the packet duplication. The information may be theaforementioned information necessary for the DU to determine to activatethe packet duplication. The present invention differs from Non-PatentDocument 19 (3GPP R2-1706716) in notifying the information from the DUto the CU.

The CU may notify the DU of whether to duplicate the packet. Thenotification may include the information on the timing to activate thepacket duplication. The information on the timing to activate the packetduplication may be identical to the information included in the responseto the notification for activating the packet duplication to betransmitted from the CU to the DU. The amount of processing for the UEto determine the timing to activate the packet duplication can bereduced.

The DU may notify the UE of the MAC signaling for activating the packetduplication. The MAC signaling may include information on the timing toactivate the packet duplication similarly to the first embodiment.

The response from the CU to the DU need not include the information onthe timing to activate the packet duplication. The MAC signaling fromthe DU to the UE need not include the information on the timing.

The processing in the UE may be identical to that in the firstembodiment. The complexity in the packet duplication which the UEperforms for the base station can be avoided.

FIG. 11 is a sequence diagram of the packet duplication when the CUdetermines to activate the packet duplication. FIG. 11 illustrates anexample using the PDCP sequence number n as the timing to activate thepacket duplication. Since the sequence illustrated in FIG. 11 includesthe same steps as those of the sequence illustrated in FIG. 10 , thesame step numbers are applied to the same Steps and the commondescription thereof is omitted.

In Step ST1201 of FIG. 11 , the DU notifies the CU of information forthe CU to determine the packet duplication. In Step ST1202, the CUdetermines to activate the packet duplication. In Step ST1203, the CUnotifies the DU of activation of the packet duplication. In Step ST1203,the CU may notify the information on the timing to activate the packetduplication. In the example of FIG. 11 , the CU notifies the DU of thePDCP sequence number n as the information.

Since Steps ST1104 to ST1111 in FIG. 11 are the same processes as thosein FIG. 10 , the description thereof is omitted.

Similarly to the first embodiment, the UE may activate/deactivate thepacket duplication at the timing of accurately receiving the MACsignaling for controlling activation/deactivation of the packetduplication. The timing of accurately receiving the MAC signaling may beafter the timing to activate/deactivate the packet duplicationinstructed via the MAC signaling. The timing after the timing toactivate/deactivate the packet duplication instructed via the MACsignaling may be, for example, the timing when the HARQ retransmissionis performed. The operations of the base station according to the firstembodiment may be read as the operations in the DU and performed. Thiscan produce the same advantages as those of the first embodiment.

Similarly to the first embodiment, the UE may activate the packetduplication retroactively. Alternatively, the timing for the UE toactivate/deactivate the packet duplication may be the packet duplicationtiming instructed by the MAC signaling for controlling theactivation/deactivation of the packet duplication, for example, thetiming to activate/deactivate the packet duplication after cyclingthrough all the numbers. This can produce the same advantages as thoseof the first embodiment.

FIG. 12 is a sequence diagram illustrating operations in thecommunication between the UE and the gNB with the CU-DU split when theUE receives the MAC signaling for activating the packet duplicationafter a specified timing due to occurrence of the HARQ retransmission.FIG. 12 illustrates an example where the DU determines to activate thepacket duplication. Since the sequence illustrated in FIG. 12 includesthe same steps as those of the sequences illustrated in FIGS. 8 and 10 ,the same step numbers are applied to the same Steps and the commondescription thereof is omitted.

Since Steps ST1101 to ST1104 in FIG. 12 are the same as those in FIG. 10, the description thereof is omitted.

Steps ST1301 to ST1304 in FIG. 12 are obtained by replacing acommunication partner of the UE from the base station to the DU in StepsST803 to ST806 in FIG. 8 , respectively. In Step ST1305, the DUtransfers, to the CU, the PDCP PDU with the PDCP sequence number n thathas been received in Step ST1304. Steps ST1307 and ST1308 are obtainedby replacing the communication partner of the UE from the base stationto the DU in Steps ST807 and ST808 in FIG. 8 , respectively.

Since Steps ST1106 to ST1111 in FIG. 12 are the same as those in FIG. 10, the description thereof is omitted.

In the first modification of the first embodiment, the DU may notify theCU of information on Ack/Nack of the MAC signaling indicating activationof the packet duplication which has been notified from the UE. This canfacilitate the system control in the CU, for example, upon occurrence ofirregularities including the excess of the number of HARQretransmissions.

The DU may notify only information on Ack which has been received fromthe UE. This can reduce the amount of signaling in the interface betweenthe CU and the DU. The DU may notify only information on Nack. This canexpedite the system control in the CU. The DU may notify information onboth of Ack and Nack. The CU can promptly obtain information on thewhole system. Alternatively, the information on Ack to be notified fromthe DU to the UE may be only the Ack initially received. The Ackinitially received may be used, for example, when the MAC signaling iscommunicated through a plurality of HARQ processes. This can furtherreduce the amount of signaling in the interface between the CU and theDU.

The method described in the first modification of the first embodimentmay be applied to deactivation of the packet duplication. The basestation with the CU-DU split can activate and deactivate the packetduplication.

The DU may set the RLC layer for duplicated packets. The DU may make thesetting immediately after determining to activate the packetduplication. Alternatively, the DU may make the setting immediatelyafter the CU notifies the DU of activation of the packet duplication.The DU can promptly activate the packet duplication even when the timeto the specified timing is short.

The DU may set the RLC layer for duplicated packets after receiving Ackfrom the UE in response to the MAC signaling for notifying the UE toactivate the packet duplication. This can minimize the time to allocatememory with the RLC setting as necessary.

The CU may instruct the DU to initialize the RLC layer. The DU mayinitialize the RLC in response to the instruction. The CU may issue theinstruction, for example, after finishing receiving, in the PDCP layerof the CU, the PDCP PDUs up to the PDCP sequence number indicating thetiming to deactivate the packet duplication. The instruction mayinclude, for example, an identifier of an RLC entity to be initialized,or an identifier of a logical channel that uses the RLC entity. Theinitialization may be, for example, initialization of a buffer in theRLC PDU, initialization of a variable to be used in the RLC entity whichis described in 7.1 of Non-Patent Document 17 (TS36.322 v14.0.0), or acombination of these two. This enables the PDCP layer of the CU toreliably receive the PDCP PDUs up to the PDCP sequence number indicatingthe timing.

Similarly to the first embodiment, the DU may change a carrierassociated with a logical channel in the packet duplication by the UEaccording to the first modification of the first embodiment. Forexample, the MAC layer of the DU may make this change. The tolerance tofluctuation in the radio environment during an activated state of thepacket duplication can be increased.

Similarly to the first embodiment, the DU may notify the UE of change inthe carrier to be used for transmitting the logical channel. Thenotification may include combined information of a logical channel and acarrier being used. The DU may notify the UE via the MAC signaling orthe L1/L2 signaling. This enables the DU to give a prompt notificationto the UE.

The DU may notify the CU of change in the carrier to be used fortransmitting the logical channel. The DU may notify the CU before,after, or simultaneously with the notification from the DU to the UE.The information included in the notification may be identical to thatincluded in the notification from the DU to the UE. The DU may notifythe CU through the interface between the CU and the DU, for example, theF1 interface. The CU may notify the DU of acknowledgement or negativeacknowledgement of change in the carrier. The interface between the CUand the DU, for example, the F1 interface may be used for thenotification of acknowledgement or negative acknowledgement. Using thenotification of acknowledgement or negative acknowledgement, the DU maynotify change in the carrier to be used for transmitting a logicalchannel from the DU to the UE. Alternatively, the DU may change thecarrier into another, restore it to the original carrier, or performanother process. Consequently, the CU can efficiently control the wholecommunication system.

The CU may change the carrier associated with the logical channel in thepacket duplication. The CU may notify the UE of change in the carriervia the RRC signaling. Alternatively, the CU may notify the DU of changein the carrier. The information included in the notification may beidentical to that included in the notification from the DU to the UE.The DU may transmit the notification to the UE. The transmission may beperformed via the MAC signaling or the L1/L2 signaling. Consequently,the CU can efficiently control the whole communication system.

Similarly to the first embodiment, the UE may enable a signaling forassociating a logical channel with a transmission carrier which is to betransmitted from the base station. The UE may enable the signaling whenthe signaling includes an SCell that is not found in the SCell list tobe used by the UE. The operations of the UE when enabling the signalingmay be identical to those according to the first embodiment. This canproduce the same advantages as those of the first embodiment.

Similarly to the first embodiment, the UE may notify the DU ofinformation on the SCell that is not found in the SCell list. The DU maynotify the CU of the information. The DU may notify the CU via theinterface between the CU and the DU. The information included in thenotification to the CU may be identical to that according to the firstembodiment.

Similarly to the first embodiment, the UE may disable the signaling forassociating a logical channel with a transmission carrier which is to betransmitted from the base station. The UE may disable the signaling whenthe signaling includes the SCell that is not found in the SCell list tobe used by the UE. The operations of the UE when disabling the signalingmay be identical to those according to the first embodiment. This canproduce the same advantages as those of the first embodiment.

Similarly to the first embodiment, the UE may notify the DU that thesignaling is disabled. The DU may notify the CU of the information. TheDU may notify the CU via the interface between the CU and the DU. Theinformation included in the notification to the CU may be identical tothat according to the first embodiment.

Since the first modification of the first embodiment enables the gNBwith the CU-DU split to receive the duplicated uplink packets, thereliability for transmitting the packets is enhanced.

The Second Embodiment

The MC (including the DC) is used as another method of the packetduplication described in the first embodiment (see Non-Patent Document 9(3GPP TR38.804 V14.0.0)).

However, none discloses switching between the packet duplication withthe CA and the packet duplication with the DC. Thus, for example, whenthe UE that has set the packet duplication with the CA to activationmoves to a cell edge, the UE has problems of failing to switch to thepacket duplication with the DC, thus failing to ensure the reliabilityof communication.

The second embodiment discloses a method for solving such problems.

The base station and the UE can mutually switch between the packetduplication with the CA and the packet duplication with the DC.

The base station and the UE may switch between the bearerconfigurations. The patterns described in Non-Patent Document 22(R2-1704001) may be used for switching between the bearerconfigurations. The base station and the UE may switch, for example,from the master cell group (MCG) bearer to the MCG split bearer. Thisenables the base station and the UE to switch from the packetduplication with the CA to the packet duplication with the DC. Theopposite pattern may be used, which enables the base station and the UEto switch from the packet duplication with the DC to the packetduplication with the CA.

As another example, the base station and the UE may switch from thesecondary cell group (SCG) bearer to the SCG split bearer. This enablesthe base station and the UE to switch from the packet duplication withthe CA to the packet duplication with the DC. The opposite pattern maybe used, which enables the base station and the UE to switch from thepacket duplication with the DC to the packet duplication with the CA.

Patterns that are not described in Non-Patent Document 22 may be used.For example, the base station and the UE may switch from the SCG bearerto a bearer in which an SCG is split into the other SCGs as anchor basestations (may be hereinafter referred to as an SCG-dedicated splitbearer). The opposite pattern may be used. These patterns can increasethe flexibility in selecting a base station in the packet duplicationwith the DC.

As another example, the base station and the UE may switch from the MCGbearer to the SCG split bearer or the SCG-dedicated split bearer. Theopposite pattern may be used. Switching between the base stations usingthe PDCP layers, that is, switching between the anchor base stationssimultaneously with switching between configurations for the packetduplication can reduce the amount of signaling.

As another example, the base station and the UE may switch from the MCGsplit bearer to the SCG bearer. The opposite pattern may be used.Switching between the base stations using the PDCP layers, that is,switching between the anchor base stations simultaneously with switchingbetween the configurations for the packet duplication can reduce theamount of signaling.

The base station and the UE may switch between logical channels. Thebase station and the UE may, for example, maintain one of the twological channels to be used for the packet duplication. The logicalchannel to be maintained may be, for example, a logical channel in whichthe same base station performs radio communication with the UE evenafter the packet duplication with the CA is switched to the packetduplication with the DC. Maintaining one of the logical channels canensure the continuity in the communication using the logical channel.

The other logical channel may be released. This can reduce the memoryusage in the base station and the UE. Alternatively, the other logicalchannel may be maintained. For example, when the packet duplication withthe original configuration is resumed due to the re-switching of thepacket duplication, the maintained logical channel may be used. This canreduce the amount of signaling in the re-switching of the packetduplication.

As another example, the base station and the UE may release both of thetwo logical channels to be used for the packet duplication. The basestation and the UE may set a new logical channel. The use resources whenthe packet duplication is switched can be flexibly set.

Alternatively, the logical channel need not be switched. The basestation and the UE may maintain the two logical channels to be used forthe packet duplication. The base station may be switched to another touse one of the logical channels as it is. This can reduce the amount ofsignaling.

To maintain the logical channels, the base station and the UE maymaintain the RLC layers. The base station and the UE may maintain theMAC layers. The base station and the UE may maintain both the RLC layersand the MAC layers. This can reduce the amount of signaling for thepacket duplication.

Alternatively, the base station and the UE may release the RLC layers.The base station and the UE may release the MAC layers. The base stationand the UE may release both the RLC layers and the MAC layers. The RLCand/or the MAC can be flexibly set.

To release the logical channels, the base station and the UE may releasethe RLC layers. The base station and the UE may release the MAC layers.The base station and the UE may release both the RLC layers and the MAClayers. This can reduce the memory usage.

The base station and the UE may release the association between alogical channel and a carrier being used in the packet duplication. Thisrelease may be used for switching from the packet duplication with theCA to the packet duplication with the DC. In switching the packetduplication from the CA to the DC, the flexibility in the carrier beingused can be improved.

The base station and the UE may specify the association between alogical channel and a carrier being used, in the packet duplication.This specification may be used for switching from the packet duplicationwith the DC to the packet duplication with the CA. The switching of thepacket duplication from the DC to the CA can be smoothly performed.

The base station and the UE may set a packet duplication operation tobeing activated. The packet duplication operation may be an operationimmediately before switching of the packet duplication. The packetduplication operation may be an operation immediately after switching ofthe packet duplication. The packet duplication operations may beoperations before and after switching of the packet duplication. Thiscan prevent an interruption in transmission/reception data before andafter the packet duplication.

The base station and the UE may set a packet duplication operation tobeing deactivated. The packet duplication operation may be an operationimmediately before switching of the packet duplication. The packetduplication operation may be an operation immediately after switching ofthe packet duplication. The packet duplication operations may beoperations before and after switching of the packet duplication. Thiscan save the radio resources before and after the packet duplication.

The base station and the UE may maintain an activation/deactivationstate of the packet duplication. The base station and the UE maymaintain the state before and after the packet duplication. For example,when the packet duplication is being activated before the packetduplication is switched, the packet duplication may be set to beingactivated even after the packet duplication is switched. This enablessmooth transmission and reception of the user data and/or the controldata.

The operation of the packet duplication in switching of the packetduplication may be predefined in a standard. Alternatively, the basestation may notify the UE of the operation. The notification may begiven via the RRC signaling, the MAC signaling, or the L1/L2 signaling.The RRC signaling may be, for example, the RRC signaling to be used forswitching the packet duplication. The MAC signaling may be, for example,the MAC signaling for activating/deactivating the packet duplicationwhich is described in the first embodiment and the first modification ofthe first embodiment. This can increase the flexibility in operationswhen the packet duplication is switched.

In the second embodiment, the master base station or the secondary basestation may activate switching of the packet duplication. Alternatively,an anchor base station may activate switching of the packet duplication.Activation of the switching of the packet duplication by the anchor basestation enables application to the SCG-dedicated split bearer.

FIG. 13 is a sequence diagram when the master base station activatesswitching of the packet duplication. FIG. 13 illustrates an example ofswitching from the packet duplication with the CA in the SCG bearer tothe packet duplication with the DC in the SCG split bearer. In FIG. 13 ,the MeNB represents an eNB that operates as the master base station, andthe SgNB represents a gNB that operates as the secondary base station.

In Step ST2001 of FIG. 13 , the UE duplicates a packet with the CA. InSteps ST2002 and ST2003, the UE transmits duplicated packets to the SgNBusing different carriers. In Step ST2004, the SgNB detects and removes aredundant packet.

In Step ST2005 of FIG. 13 , the MeNB transmits an SgNB modificationrequest to the SgNB. The SgNB modification request may includeinformation indicating a type of the packet duplication. The informationindicating the type of the packet duplication may be included in theSgNB modification request included in, for example, SCG-ConfigInfo.

In Step ST2006 of FIG. 13 , the SgNB transmits an SgNB modificationrequest acknowledgement to the MeNB. The SgNB modification requestacknowledgement may include information on change in the RRC parameterof the UE. The information on change in the RRC parameter of the UE maybe included in the SgNB modification request acknowledgement includedin, for example, SCG-Config.

Although FIG. 13 illustrates an example acknowledgement in response tothe SgNB modification request, the acknowledgement may be replaced witha negative acknowledgement. For example, the SgNB may transmit an SgNBmodification request rejection to the MeNB. The SgNB modificationrequest rejection may include a cause for rejection. Alternatively, theSgNB modification request rejection may include information on a bearer,for example, an identifier of the bearer. The bearer may be a bearerthat causes the SgNB to reject the request. In response to the negativeacknowledgement, the MeNB may change the setting parameter, and notifythe SgNB modification request again. This enables, for example, the MeNBto perform smooth processes when the SgNB cannot satisfy the requestfrom the MeNB.

In Step ST2007 of FIG. 13 , the MeNB notifies the UE of the RRCconnection reconfiguration (RRCConnectionReconfiguration). The UEswitches the packet duplication and changes the RRC parameter tocorrespond to the switching, using Step ST2007. In Step ST2008, the UEgives the MeNB the RRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification. In Step ST2009, theMeNB gives the SgNB the SgNB reconfiguration complete notification.

In Step ST2010 of FIG. 13 , the UE duplicates a packet with the DC. InSteps ST2011 and ST2012, the UE transmits the duplicated packets to theMeNB and the SgNB, respectively. In Step ST2013, the MeNB transmits, tothe SgNB, the packet received in Step ST2011. In Step ST2014, the SgNBdetects and removes a redundant packet.

Although FIG. 13 exemplifies that the master base station is the eNB andthe secondary base station is the gNB, the master base station may be agNB. The secondary base station may be an eNB. Both the master andsecondary base stations may be the gNBs or the eNBs.

FIG. 14 is a sequence diagram when the secondary base station activatesswitching of the packet duplication. FIG. 14 illustrates an example ofswitching from the packet duplication with the CA in the SCG bearer tothe packet duplication with the DC in the SCG split bearer. In FIG. 14 ,the MeNB represents an eNB that operates as a master base station, andthe SgNB represents a gNB that operates as a secondary base station.Since FIG. 14 includes the same steps as those of the sequenceillustrated in FIG. 13 , the same step numbers are applied to the sameSteps and the common description thereof is omitted.

In Step ST2101 of FIG. 14 , the SgNB transmits an SgNB modificationrequired notification to the MeNB. The notification may include theinformation indicating the type of the packet duplication. Thenotification may include the information on change in the RRC parameterof the UE. The information indicating the type of the packet duplicationand/or the information on change in the RRC parameter of the UE may beincluded in the notification included in, for example, SCG-Config.

Although FIG. 14 exemplifies that the MeNB acknowledges the SgNBmodification required notification from the SgNB, the MeNB may refuseit. For example, the MeNB may transmit an SgNB modification refusal tothe SgNB. The SgNB modification refusal may include a cause for therefusal. Alternatively, the SgNB modification refusal may includeinformation on a bearer, for example, an identifier of the bearer. Thebearer may be a bearer that causes the MeNB to refuse the request. Forexample, in response to the negative acknowledgement, the SgNB maychange the setting parameter and notify the SgNB modification requestagain. This enables, for example, the SgNB to perform smooth processeswhen the MeNB cannot satisfy the request from the SgNB.

In Step ST2102 of FIG. 14 , the MeNB notifies the SgNB of an SgNBmodification confirmation.

Similarly to FIG. 13 , the master base station may be the gNB in FIG. 14. The secondary base station may be the eNB. Both the master andsecondary base stations may be the gNBs or the eNBs.

The SgNB modification request to be transmitted from the master basestation to the secondary base station may include the informationindicating the type of the packet duplication. The type of the packetduplication may be, for example, the packet duplication with the CA orthe packet duplication with the DC. The information indicating the typeof the packet duplication may be information indicating a type after thepacket duplication is switched.

The master base station may include the information indicating the typeof the packet duplication, into items for setting additional bearers.The items for setting additional bearers may be, for example, equivalentto setting items of the SCG bearer and the split bearer in “E-RABs To BeAdded Item” in 9.1.3.5 of Non-Patent Document 23 (3GPP TS36.423v14.3.0). Inclusion in the items for setting additional bearers enables,for example, switching from the packet duplication with the CA in theMCG bearer to the packet duplication with the DC.

As another example, the master base station may include the informationindicating the type of the packet duplication, into items for settingmodified bearers. The items for setting modified bearers may be, forexample, equivalent to setting items of the SCG bearer and the splitbearer in “E-RAB s To Be Modified Item” in 9.1.3.5 of Non-PatentDocument 23 (3GPP TS36.423 v14.3.0). Inclusion in the items for settingmodified bearers enables, for example, switching from the packetduplication with the CA in the SCG bearer to the packet duplication withthe DC in the SCG split bearer.

As another example, the master base station may include the informationindicating the type of the packet duplication, into items for settingreleased bearers. The items for setting released bearers may be, forexample, equivalent to setting items of the SCG bearer and the splitbearer in “E-RABs To Be Released Item” in 9.1.3.5 of Non-Patent Document23 (3GPP TS36.423 v14.3.0). Inclusion in the items for setting releasedbearers enables, for example, switching from the packet duplication withthe DC to the packet duplication with the CA in the MCG bearer.

The secondary base station may determine whether to duplicate thepacket, using the information indicating the type of the packetduplication. For example, the secondary base station may determine notto duplicate the packet when the information is not included.

Alternatively, a value indicating no packet duplication may be added tothe information. Since this enables collective handling whether toduplicate the packet, the amount of processing can be reduced.

Setting items on the PDU session to be added or setting items on theradio bearer to be added may replace “E-RABs To Be Added Item”. Thesetting items on the PDU session to be added and/or the setting items onthe radio bearer to be added may be newly added. The same may apply to“E-RABs To Be Modified Item” and “E-RABs To Be Released Item”. Themethods described in the second embodiment are applicable even when themaster base station is the MgNB. The flexible settings are possible foreach PDU session and/or for each radio bearer.

The setting items in the split bearer may be setting items in the MCGsplit bearer, setting items in the SCG split bearer, or a combination ofthese two. The setting items in the split bearer may include informationindicating a type of the split bearer. The type of the split bearer maybe the MCG split bearer, the SCG split bearer, or the SCG-dedicatedsplit bearer. The complexity of design in the interface between the basestations can be avoided.

Alternatively, the setting items in the split bearer may be split into(a) the setting items in the MCG split bearer, (b) the setting items inthe SCG split bearer, and (c) the setting items in the SCG-dedicatedsplit bearer. Batch processing on the bearers of the same type canreduce the amount of processing.

The SgNB modification request to be transmitted from the master basestation to the secondary base station may include an identifier of aradio bearer. The identifier of the radio bearer may be included in theitems for setting additional bearers, the items for setting modifiedbearers, or the items for setting released bearers. The secondary basestation can uniquely identify a bearer, which can prevent themalfunctions.

The SgNB modification request to be transmitted from the master basestation to the secondary base station may include an identifierindicating maintaining or releasing of a logical channel, an identifierindicating a logical channel to be maintained, and an identifierindicating a logical channel to be released. This enables flexibleswitching of the packet duplication for each logical channel.

The SgNB modification request to be transmitted from the master basestation to the secondary base station may include a cause formodification. The cause may include information indicating the packetduplication. The information indicating the packet duplication may beinformation indicating setting start of the packet duplication,information indicating setting change in the packet duplication, orinformation indicating release of the packet duplication. Theinformation may be added to the list of causes described in 9.2.6 ofNon-Patent Document 23 (3GPP TS36.423 v14.3.0). The information may beadded to, for example, Radio Network Layer in the list of causes oranother part. This enables the secondary base station to smoothlyperform processes for the packet duplication.

The SgNB modification request acknowledgement to be transmitted from thesecondary base station to the secondary base station may include anidentifier of a bearer. The identifier of the bearer may be a bearer onswitching the packet duplication.

Similarly to the SgNB modification request, the secondary base stationmay include the identifier of the bearer in the items for settingadditional bearers, the items for modified bearers, or the items forreleased bearers. The items for setting additional bearers, the itemsfor modified bearers, and the items for released bearers may be, forexample, equivalent to setting items of the SCG bearer and the splitbearer in “E-RAB s Admitted To Be Added Item”, and “E-RABs Admitted ToBe Modified Item”, and “E-RABs Admitted To Be Released Item”,respectively, in 9.1.3.6 of Non-Patent Document 23 (3GPP TS36.423v14.3.0). This enables a bearer to be identified in switching the packetduplication.

Alternatively, the secondary base station may include the identifier ofthe bearer in a list of non-admitted bearers. The list of non-admittedbearers may be, for example, equivalent to “E-RABs Not Admitted List” in9.1.3.6 of Non-Patent Document 23 (3GPP TS36.423 v14.3.0). A list ofnon-admitted PDU sessions or a list of non-admitted radio bearers mayreplace the “E-RABs Not Admitted List”. Consequently, the master basestation can control the non-admitted bearers.

The setting items on the PDU session to be added or the setting items onthe radio bearer to be added may replace the “E-RABs Admitted To BeAdded Item”. The setting items on the PDU session to be added and/or thesetting items on the radio bearer to be added may be newly added. Thesame may apply to the “E-RABs Admitted To Be Modified Item” and the“E-RABs Admitted To Be Released Item”. The method described in thesecond embodiment is applicable even when the master base station is theMgNB. The flexible settings are possible for each PDU session and/or foreach radio bearer.

The setting items in the split bearer may be the setting items in theMCG split bearer, the setting items in the SCG split bearer, or acombination of these two. The setting items in the split bearer mayinclude information indicating a type of the split bearer. The type ofthe split bearer may be the MCG split bearer, the SCG split bearer, orthe SCG-dedicated split bearer. The complexity of design in theinterface between the base stations can be avoided.

Alternatively, the setting items in the split bearer may be split into(a) the setting items in the MCG split bearer, (b) the setting items inthe SCG split bearer, and (c) the setting items in the SCG-dedicatedsplit bearer. Batch processing on the bearers of the same type canreduce the amount of processing.

The secondary base station may include information on the packetduplication in the SgNB modification request acknowledgement. Theinformation on the packet duplication may be included in a partidentical to that of the identifier of the bearer, or a part indicatinga setting item for the UE, for example, SCG-Config.

The information on the packet duplication may be information indicatingwhether to duplicate the packet, the information indicating the type ofthe packet duplication, or combined information of the two. For example,the information indicating the type of the packet duplication mayinclude information indicating no packet duplication.

Alternatively, the information on the packet duplication may includeinformation on logical channels, information on the RLC setting, orinformation on radio carriers. The information on the packet duplicationmay be combined information of at least two of these pieces ofinformation.

The information on the packet duplication may be included in informationon radio bearers. The information on the packet duplication may beincluded in a list of bearers to be added/modified in Non-PatentDocument 24 (3GPP TS36.331 v14.3.0), for example, a part equivalent toDRB-ToAddModListSCG-r12. The part may include an identifier of a logicalchannel and the information on the RLC setting in combination, as, forexample, packetdupListSCG. The combination may include the informationon radio carriers. This enables the packet duplication with the CA.

The number of combinations included in the packetdupListSCG may be one.The combination may include an identifier of a logical channel and theinformation on the RLC setting. The combination may be the setting ofthe secondary base station side in the packet duplication with the DC.Alternatively, the number of combinations included in thepacketdupListSCG may be two. The combination may include an identifierof a logical channel, the RLC setting, and the information on radiocarriers. The combination may be applied to the packet duplication withthe CA in the SCG bearer.

Alternatively, the information on the packet duplication may be includedin a list of bearers to be released in Non-Patent Document 24 (3GPPTS36.331 v14.3.0), for example, a part equivalent toDRB-ToReleaseListSCG-r12. This enables, for example, switching from thepacket duplication with the DC to the packet duplication with the CA inthe MCG bearer.

Alternatively, information on a combination of a logical channel and aradio carrier may be included in items for setting the MAC, for example,a part equivalent to MAC-MainConfig in Non-Patent Document 24 (3GPPTS36.331 v14.3.0). This can reduce the amount of processing in the MAClayer.

The information on the packet duplication may be information on thepacket duplication in the SRBs. For example, the information on thepacket duplication in the SRBs may be included in the SCG-Config. Thiscan enhance the reliability of communication in the C-Plane.

Information included in the SgNB modification required notification tobe transmitted from the secondary base station to the master basestation may be identical to that included in the SgNB modificationrequest acknowledgement. The complexity of design on the switching ofthe packet duplication can be avoided.

Information included in the SgNB reconfiguration complete notificationto be transmitted from the master base station to the secondary basestation may be identical to that included in the SgNB modificationrequest acknowledgement. The SCG-Config in the SgNB modification requestacknowledgement may be read as the SCG-ConfigInfo. The complexity ofdesign on the switching of the packet duplication can be avoided.

Information included in the SgNB modification confirmation notificationto be transmitted from the master base station to the secondary basestation may be identical to that included in the SgNB reconfigurationcomplete notification previously described. The complexity of design onthe switching of the packet duplication can be avoided.

The RRC connection reconfiguration to be transmitted from the masterbase station to the UE may include the information on the packetduplication. The information on the packet duplication may be identicalto that included in the SgNB modification request acknowledgement. Themaster base station may add the RRC setting on the communication withthe master base station, to the information on the packet duplication.The RRC setting on the communication with the master base station may bethe setting on the packet duplication using the master base station.

The master base station may include the information on the packetduplication as, for example, the packetdupListSCG previously described.The number of combinations included in the packetdupListSCG may be two.Each of the combinations may include an identifier of a logical channeland the information on the RLC setting. Each of the combinations mayinclude the information on radio carriers. Inclusion of the informationon radio carriers enables the packet duplication with the CA. Both ofthe pieces of the information included in the combination may have thesetting in the communication between the UE and the master base station.This enables the packet duplication with the CA in the MCG bearer. Oneof the pieces of the information may have the setting in thecommunication between the UE and the master base station, whereas theother of the information may have the setting in the communicationbetween the UE and the secondary base station. This enables the packetduplication with the DC. Alternatively, both of the pieces of theinformation may have the setting in the communication between the UE andthe secondary base station. This enables the packet duplication with theCA in the SCG bearer.

The method for switching the packet duplication which is described inthe second embodiment may be applied to the setting or releasing of thepacket duplication. The use of the shared signaling on the packetduplication can avoid the design complexity.

The method for switching the packet duplication which is described inthe second embodiment may be applied to the multi-connectivity. This canenhance the reliability in transmission and reception with themulti-connectivity.

In the packet duplication with the multi-connectivity, a split bearerthat routes two base stations may be used. The RRC connectionreconfiguration to be notified from the master base station to the UEmay include the information on the packet duplication. The informationmay include information for identifying the SCG. An identifier of theSCG may be newly provided or an identifier of the secondary base stationmay be used, as the information. The UE may identify the SCG from anidentifier of a cell belonging to the SCG. The identifier of the cellmay be, for example, an identifier of the PSCell, or an identifier ofthe SCell in the SCG.

In the packet duplication with the multi-connectivity, a split bearerthat routes three or more base stations may be used. The RRC connectionreconfiguration to be notified from the master base station to the UEmay include the information on the packet duplication. The informationmay include the information for identifying the SCG. The information onthe packet duplication may include three or more combinations eachconsisting of an identifier of a logical channel and the information onthe RLC setting. For example, the information may include three or morecombinations included in the packetdupListSCG. Each of the combinationsmay include a logical channel and the RLC setting which are used in eachbase station.

In the packet duplication with the multi-connectivity, the UE mayactivate/deactivate the packet duplication via the MAC signaling fromany of the base stations. The MAC signaling may include information on alogical channel to be activated/deactivated. Information on a basestation using the logical channel may be used. The information on thebase station may be an identifier of the base station, for example, agNB-ID, an identifier of the PCell or the PSCell, an MCG-ID, or anSCG-ID. An MCG-ID and/or an SCG-ID may be newly provided. Thisfacilitates activation/control of the packet duplication in the UE.

Alternatively, the base station using each logical channel maydedicatedly notify the UE to activate/deactivate the logical channel viathe MAC signaling. This can reduce the amount of MAC signaling.

The information on a logical channel need not be included in the secondembodiment. The information on a logical channel need not be included,for example, in the setting of the packet duplication with the DC or inswitching the setting to the packet duplication with the DC. This canreduce the size of the signaling.

In the second embodiment, the UE may receive signals from all the basestations that configure the DC/MC. The signals may be, for example, theMAC signaling. This facilitates the packet duplication control.

The UE may receive signals from all the carriers which the UE uses ineach base station. The signals may be, for example, the MAC signaling.This can increase the flexibility of the scheduling in the base station.Alternatively, the UE may receive a signal from a part of the carrierswhich the UE uses in each base station, for example, the MAC signaling.The part of the carriers may be, for example, the PCell or the PSCell.The base station and the UE may transmit and receive the MAC signalingthrough the PCell and/or the PSCell. The power consumption of the UE canbe reduced.

Alternatively, the UE may receive a signal from the base station thattransmits a packet during an activated state of the packet duplication,for example, the MAC signaling in the second embodiment. The powerconsumption of the UE can be reduced.

The UE may receive the signals from all the carriers which the UE usesin each base station, for example, the MAC signaling. This can increasethe flexibility of the scheduling in the base station. Alternatively,the UE may receive the signals from a part of the carriers which the UEuses in each base station, for example, the MAC signaling. The part ofthe carriers may be, for example, the PCell or the PSCell. The basestation and the UE may transmit and receive the MAC signaling throughthe PCell and/or the PSCell. The power consumption of the UE can befurther reduced.

Alternatively, the UE may receive a signal from the master base station,for example, the MAC signaling in the second embodiment. This can reducethe power consumption in the UE, and facilitates the control in themaster base station.

The UE may receive the signals from all the carriers which the UE usesin the master base station, for example, the MAC signaling. This canincrease the flexibility of the scheduling in the master base station.Alternatively, the UE may receive the signals from some of the carrierswhich the UE uses in the master base station, for example, the MACsignaling. Some of the carriers may be, for example, the PCell. The basestation and the UE may transmit and receive the MAC signaling throughthe PCell. The power consumption of the UE can be further reduced.

The second embodiment enables the switching between the packetduplication with the CA and the packet duplication with the DC. Forexample, the reliability in the communication when the UE is moving canbe ensured. Moreover, the throughput can be increased.

The Third Embodiment

When the packet duplication is deactivated, clearing data in the RLClayer has been proposed (see Non-Patent Document 20 (R2-1704836)). Ithas been proposed that in the downlink packet duplication, the basestation does not control activation/deactivation of the UE (seeNon-Patent Document 21 (R2-1702753)).

In the RLC-AM, the RLC entities in the transmitter and the receiver areintegrated (see Non-Patent Document 17 (TS36.322 v14.0.0)).

However, in the packet duplication using the RLC-AM, for example, thepacket duplication in the SRBs, deactivation of the uplink packetduplication causes a problem of clearing a buffer of the RLC layer inthe downlink packet duplication.

The third embodiment discloses a method for solving such a problem.

The UE clears only the buffer at the transmitter in the RLC-AM. The basestation clears only the buffer at the transmitter in the RLC-AM. The UEand/or the base station may clear the buffer upon deactivation of theuplink packet duplication.

The UE may clear a variable and a transmission window at the transmitterin the RLC-AM.

As an alternative method, the base station simultaneously controls thepacket duplication in the downlink and the uplink. The simultaneouscontrol of the downlink and the uplink may be applied to the packetduplication using the RLC-UM and/or the RLC-TM.

This method described in the third embodiment can prevent thedeactivation of the uplink packet duplication from clearing the bufferin the downlink packet duplication. This can ensure the continuity inthe data.

The Fourth Embodiment

In NR, an RRC_INACTIVE state has been newly introduced as a state of theUE (see Non-Patent Document 9 (3GPP TR38.804 V14.0.0)). In NR,supporting small data transmission from the UE in the RRC_INACTIVE statehas been proposed (see Non-Patent Document 9 (3GPP TR38.804 V14.0.0)).

However, regarding the small data transmission from the UE in theRRC_INACTIVE state, whether the packet duplication described in thefirst and second embodiments is supported has not yet been discussed.Thus, when the UE that performs transmission with the packet duplicationtransitions to the RRC_INACTIVE state, the UE does not know the smalldata transmission method and has a problem of failing to transmit datato the base station.

The fourth embodiment discloses a method for solving such a problem.

The UE does not support the packet duplication in the RRC_INACTIVEstate.

The UE may retain the setting of the packet duplication. The UE mayretain the setting when transitioning to the RRC_INACTIVE state. Thesetting may be the setting on the packet duplication with the DC or thesetting on the packet duplication with the CA.

When transitioning to RRC_CONNECTED again, the UE can promptly resumethe packet duplication.

The UE may deactivate the packet duplication. The UE may deactivate thepacket duplication when transitioning to the RRC_INACTIVE state. The UEmay autonomously deactivate the packet duplication. Alternatively, thebase station or the master base station may instruct the UE todeactivate the packet duplication. The MAC signaling for deactivatingthe packet duplication which is described in the first embodiment may beapplied to the instruction. Alternatively, the instruction may beincluded in an instruction for transitioning to the RRC_INACTIVE statefrom the base station or the master base station to the UE.

The UE may release the setting of the packet duplication. The UE mayrelease the setting when transitioning to the RRC_INACTIVE state. The UEmay autonomously release the setting. Alternatively, the base station orthe master base station may instruct the UE to release the setting. TheUE may release the setting on the packet duplication simultaneously whenreleasing the setting of the DC or the setting of the CA. This canreduce the memory usage of the UE in the RRC_INACTIVE state.

As another example, the base station or the master base station maynotify the UE to maintain/release the setting of the packet duplication.The base station or the master base station may include the notificationof maintaining/releasing of the setting, in the instruction for the UEto transition to the RRC_INACTIVE state. For example, an identifierindicating whether to maintain or release the setting of the packetduplication may be included in the instruction. Consequently, the basestation or the master base station can, for example, make flexiblesettings according to a radio channel state.

The base station or the master base station may set, for each bearer,whether to maintain or release the setting of the packet duplication.This enables flexible operations of the packet duplication for eachbearer.

The following four examples (1) to (4) are disclosed as methods fornotifying, from the base station or the master base station to the UE,whether to maintain or release the setting of the packet duplication foreach bearer:

(1) determined in a standard;

(2) common signaling;

(3) dedicated signaling; and

(4) combinations of (1) to (3) above.

In (1), for example, whether to maintain or release the setting may bedetermined for each bearer type. For example, the setting of the packetduplication may be maintained in the SRBs, and the setting of the packetduplication may be released in the DRBs. Alternatively, for example, thesetting of the packet duplication may be maintained in the SRB0 and theSRB2, and the setting of the packet duplication may be released in theSRB1, the SRB3, and the DRBs. This can reduce the amount of signaling.

In (2), the base station or the master base station may notify whetherto maintain or release the setting, using system information. This canreduce the amount of signaling.

In (3), the base station or the master base station may notify whetherto maintain or release the setting, using, for example, theRRC-dedicated signaling. The RRC-dedicated signaling may be aninstruction for the UE to transition to the RRC_INACTIVE state, oranother RRC-dedicated signaling. The RRC-dedicated signaling may includean identifier of a bearer for maintaining the setting of the packetduplication, an identifier of a bearer for releasing the setting of thepacket duplication, or both of the identifiers. Whether to maintain orrelease the packet duplication can be flexibly set for each bearer.

In (3), whether to maintain or release the setting of the packetduplication may be notified for each bearer type. The details on whetherto maintain or release the packet duplication for each bearer type maybe similar to those described above (1). The flexible setting ispossible for each bearer type.

In (4), whether to maintain or release the setting of the packetduplication, for example, in each of the SRB s may be defined in astandard. The base station or the master base station may dedicatedlynotify the UE of whether to maintain or release the setting of thepacket duplication in each of the DRBs. This can increase theflexibility of the setting for each of the DRBs as well as reducing theamount of signaling.

The UE may perform the small data transmission using the packetduplication. The UE may perform the small data transmission aftertransitioning to the RRC_CONNECTED state. The UE may maintain thesetting of the packet duplication. The UE may maintain the setting aftertransitioning to the RRC_INACTIVE state. This facilitates the controlover the UE on transmission of data.

The UE may activate the packet duplication. The UE may activate thepacket duplication after transitioning to the RRC_CONNECTED state. TheUE may autonomously activate the packet duplication. For example, the UEmay activate the packet duplication using information indicating anactivation/deactivation state of the packet duplication which isdescribed in the first embodiment. Alternatively, the UE may activatethe packet duplication, using an instruction for activating the packetduplication from the base station or the master base station. Theinstruction for activating the packet duplication may be included in aninstruction for transitioning to RRC_CONNECTED from the base station orthe master base station to the UE or notified separately from theinstruction for transitioning to RRC_CONNECTED. The base station or themaster base station may notify the UE of the instruction for activatingthe packet duplication via the MAC signaling described in the firstembodiment.

The UE may release the setting of the packet duplication uponreselection of a cell. Alternatively, the UE may release the setting ofthe packet duplication upon transitioning to an RRC_IDLE state. The UEmay release the setting autonomously or using an instruction from thebase station or the master base station. This can reduce the memoryusage of the UE upon reselection of a cell and/or in the RRC_IDLE state.

The fourth embodiment can prevent an operating error in the UE on thesmall data transmission during an INACTIVE time.

The Fifth Embodiment

In transmission of data to the secondary base station in theRRC_INACTIVE state which is described in the fourth embodiment, addingthe SCG after restoration from the RRC_INACTIVE state and thentransmitting the data to the secondary base station has been proposed(see Non-Patent Document 25 (R2-1704425)). As an alternative method, anearly SCG bearer configuration for adding the SCG simultaneously withrestoration from the RRC_INACTIVE state has been proposed (seeNon-Patent Document 26 (R2-1704420)).

The two methods, however, cause a problem of delay in starting totransmit data from the UE to the secondary base station, because the UEwaits for the SCG being added and then transmits the data to thesecondary base station.

The fifth embodiment discloses a method for solving such a problem.

The UE transmits data to the secondary base station through the masterbase station. The data may be data to be transmitted using the SCG splitbearer. The master base station transfers the data to the secondary basestation. The master base station may transfer the data through aninterface between the base stations, for example, the X2 interface.

In the fifth embodiment, the master base station may switch from the SCGbearer to the SCG split bearer. The master base station may notify thesecondary base station of a request for the switching. The secondarybase station may notify the master base station of a response to therequest. The master base station may perform the switchingsimultaneously when instructing the UE to transition to the RRC_INACTIVEstate or separately from the instruction for transitioning the state.The master base station may include the switching instruction, in theinstruction for the UE to transition to the RRC_INACTIVE state. Theswitching instruction may include an identifier of the SCG bearer. Thisenables the UE to promptly transmit data to the secondary base stationalso in the SCG bearer.

FIG. 15 is a sequence diagram illustrating the small data transmissionfrom the UE in the RRC_INACTIVE state to the secondary base station.FIG. 15 exemplifies that the master base station is the eNB and thesecondary base station is the gNB. The master base station may be thegNB. The secondary base station may be the eNB. Although FIG. 15exemplifies that the UE transitions to the RRC_CONNECTED state after thesmall data transmission, the UE may maintain the RRC_INACTIVE state.

In Step ST3001 of FIG. 15 , the UE in the RRC_INACTIVE state starts arandom access procedure for the master base station. In Step ST3001, theUE transmits a random access preamble (RA preamble) to the master basestation. In Step ST3002, the master base station transmits a randomaccess response (RA response) to the UE. The response includes an uplinkgrant to the UE.

In Step ST3003 of FIG. 15 , the UE transmits the RRC connection resumerequest (RRCConnectionResumeRequest) to the master base station.

In Step ST3005 of FIG. 15 , the UE transmits, to the master basestation, the uplink data for the secondary base station. In Step ST3006,the master base station transmits the uplink data to the secondary basestation.

In Step ST3007 of FIG. 15 , the master base station gives the UE the RRCconnection resumption (RRCConnectionResume) notification. In StepST3008, the UE gives the master base station the RRC connectionresumption complete (RRCConnectionResumeComplete) notification. The UEtransitions to the RRC_CONNECTED state in Step ST3008.

The method disclosed in the fifth embodiment enables the UE in theINACTIVE state to promptly transmit data to the secondary base station.

The Sixth Embodiment

The MC has been proposed as the 5G technology in the 3GGP (seeNon-Patent Document 27 (R2-167583)). Configuring the connection of oneUE to one master base station and a plurality of secondary base stationshas been discussed as the MC. Moreover, support of the MCG split bearerand the SCG bearer has been proposed as the MC. A group of MeNB cells isreferred to as the MCG. A group of SgNB cells is referred to as the SCG.

However, none discloses, in the MC using two or more secondary basestations, architecture including a high-level NW device (hereinafteralso referred to as a high-level NW) and a method for setting the MC,for example, how to set the two or more secondary base stations. Thesixth embodiment discloses an architecture including the high-level NW,and a method for setting the MC.

FIG. 16 illustrates an architecture of the MC. FIG. 16 illustrates thatthe high-level NW is an EPC, the master base station is a base stationin the LTE (eNB), and the secondary base stations are base stations inNR (gNBs). The master base station in the LTE is referred to as theMeNB, and the secondary base stations in NR are referred to as theSgNBs. The protocol configuration of the eNB includes the PDCPs, theRLCs, the MAC, and the PHY. The protocol configuration of the gNBconsists of the New AS sublayer, the PDCP, the RLCs, the MAC, and thePHY. The New AS sublayer is set higher than the PDCP.

Although FIG. 16 illustrates the architecture on the base station side,the architecture on the UE side is identical to that on the base stationside except for the high-level NW. One UE includes the RLC, the MAC, andthe PHY for the MeNB, the RLC, the MAC, and the PHY for each of SgNBsset for the MC, and the PDCP.

FIG. 16 illustrates the use of the MCG split bearer. The high-level NWis connected to the MeNB, and the SgNBs for the MC are connected to theMeNB. The PDCPs of the MeNB process the downlink data. Even when thenumber of SgNBs is more than one, the PDCPs assign one serial sequencenumber (SN) to each data. The data to which the SN is assigned is splitinto the MeNB and the SgNBs. The pieces of split data are transmitted tothe RLCs in the MeNB and the SgNBs, processed by the RLCs, the MACs, andthe PHYs in the MeNB and SgNBs, and transmitted to the UE.

The pieces of data received by the UE from the MeNB and the SgNBs areprocessed by the PHYs, the MACs, and the RLCs for the MeNB and theSgNBs, and then transferred to the PDCP. The PDCP performs reorderingbased on the SNs assigned to the pieces of the data transferred fromlayers for the MeNB and the SgNBs, and transfers the pieces of data tothe upper layer.

The PDCP in the UE processes the pieces of data from the upper layer asthe uplink data. Similarly in the downlink, even when the number ofSgNBs is more than one, the PDCP assigns one serial sequence number (SN)to each data in the uplink. The data to which the SN is assigned issplit into the RLCs for the MeNB and the SgNBs to be transferred. Thepieces of transferred data are processed by the RLCs, the MACs, and thePHYs for the MeNB and the SgNBs, and transmitted to the MeNB and theSgNBs.

The pieces of data received by the MeNB and the SgNBs from the UE areprocessed by the PHYs, the MACs, and the RLCs for the MeNB and theSgNBs, and then transferred to the PDCP of the MeNB. The PDCP of theMeNB performs reordering based on the SNs assigned to the pieces ofdata, and transfers the pieces of data to the high-level NW.

A method for setting a plurality of SCGs for the MC is disclosed. TheMeNB sets, to the UE, the SCGs for the MC. A radio bearer for performingthe MC is set in the setting of the SCGs. The setting should be notifiedvia the RRC signaling.

The SCGs are set one by one. The settings of the plurality of SCGs forthe MC are made using one setting of the SCG. The one setting of the SCGshould be made as many as the number of the SCGs for the MC. Thesignaling for setting the SCG is performed as many as the number of theSCGs which the MeNB sets to the UE. Since the number of the SCGs to beconnected in the DC is only one, the SCG previously set needs to bereleased when the other SCGs are connected while the one SCG is set.Aside from this, an additional setting of the SCG is made withoutreleasing the SCG previously set. This enables the MeNB to set aplurality of SCGs to the UE.

Information indicating the additional SCG setting while the previous SCGsetting is maintained may be provided. The MeNB notifies the UE of theinformation. The MeNB may include the information in the SCG setting tobe notified. As an alternative method, a signaling for the additionalSCG setting while the previous SCG setting is maintained may beprovided. In the presence of the one SCG setting by the MeNB with theadditional signaling, the UE can recognize the setting as the additionalSCG setting while the previous SCG setting is maintained.

For example, the RRCConnectionReconfiguration for setting the RRCconnection may be used as the RRC signaling. For example,SCG-ConfigPartSCG in the signaling may include an SCG configuration, anda bearer configuration for performing the MC. Examples of the bearerconfiguration include a bearer identifier, and an AS setting for thebearer.

In the DC, the MCG and only one SCG are set per bearer. When a pluralityof SCGs are set in the MC, the plurality of SCGs may be set per bearer.In the settings of the SCG configurations from the second time onward,the bearer set with the previous SCG configurations may be used. Thesame bearer identifier may be set. Consequently, the UE can recognizethat a plurality of SCG configurations are set to the bearer.

The setting of the bearer may differ for each SCG for the MC. When thebearer identifier set with the previous SCG configurations is set in thesettings of the SCG configurations from the second time onward, one or aplurality of parameters of AS setting for the bearer with the beareridentifier previously set may be omitted. When the parameters areomitted, the parameter of the AS setting for a bearer with the samebearer identifier is used.

SCG identifiers may be provided. The SCG identifiers may be included asinformation on the SCG configuration for the SCG setting. The SCGs withthe same AS parameter for bearer may be set using the SCG identifiers.For example, the SCG identifiers are included in the bearerconfiguration. This enables the UE to recognize that the bearerconfiguration set to the SCGs is the bearer configuration set to theSCGs indicated by the SCG identifiers. Consequently, the AS parameterfor bearer which is set to the SCGs can be identical to the AS parameterfor bearer which is set to an arbitrary SCG.

Consequently, when the AS parameters for bearer to be set to therespective SCGs for the MC are the same, the parameters can be omittedor set with less amount of information. The radio resources necessaryfor the MeNB to notify the UE can be reduced.

Although the assignment of the SCG identifier is disclosed, an SgNBidentifier may be assigned. An identifier indicating a pair of SCGs orSgNBs may be assigned. Assignment of such an identifier enables the UEto recognize the setting not for each cell but for each SgNB or eachSgNB pair when the MC is set to many SgNBs. This is effective when thesetting is changed for each SgNB or for each SgNB pair. This reducesinformation to be notified from the MeNB to the UE.

FIGS. 17 and 18 illustrate an example sequence for setting the MC. FIGS.17 and 18 are connected across a location of a border BL 1718. FIGS. 17and 18 illustrate the use of the MeNB and two SgNBs (SgNB 1 and SgNB 2).FIGS. 17 and 18 illustrate the use of the MCG split bearer. In StepST4201, data is communicated between the UE and the MeNB. In StepST4202, the MeNB determines to perform the DC for the UE. The methoddisclosed in Non-Patent Document 1 (TS36.300) should be applied to DCsetup processing. Steps ST4203 to ST4213 illustrate the DC setupprocessing.

In Step ST4210, the MeNB routes data into its own MeNB and the SgNB 1 towhich the DC has been set. Since the number of secondary base stationsto be connected is one, data from the high-level NW is processed by thePDCP of the MeNB, and split into its own MeNB and the SgNB 1 to betransferred, similarly to the conventional DC. Data received by its ownMeNB and the SgNB 1 from the UE is transferred to the MeNB, processed bythe PDCP of the MeNB, and transferred to the high-level NW.

The same applies to the UE side.

In Step ST4214, the MeNB determines to set the MC to the UE. The MeNBdetermines to connect the UE to the SgNB 2 while maintaining theconnection of the UE to the SgNB 1. In Step ST4215, the MeNB notifiesthe SgNB 2 of an SgNB addition request. Step ST4203 in the DC setupprocessing may be applied to this signaling. The MeNB may make thebearer setting of the SgNB 2 which is requested to be added, identicalto the bearer setting of its own eNB (MeNB). Alternatively, the MeNB maydetermine the bearer setting of the SgNB 2 in consideration of thebearer settings of its own eNB (MeNB) and the SgNB 1. The bearer forperforming the MC should be set so that the QoS set by the high-level NWis satisfied.

The SgNB 2 determines the AS setting according to the bearer settingindicated by the SgNB addition request from the MeNB. In Step ST4216,the SgNB 2 notifies the MeNB of the determined AS setting. In StepST4217, the MeNB notifies the UE of the settings of the MC. As thesettings of the MC, the MeNB notifies the SCG configuration of the SgNB2 to be added and the bearer configuration for performing the MC. TheRRCConnectionReconfiguration for setting the RRC connection may be usedas the signaling.

In Step ST4217, the MeNB may notify the UE of the information indicatingthe additional SCG setting while the previous SCG setting of the SgNB 1is maintained. With the information specified, the UE can clearlyrecognize the setting for connection to the SgNB 2 with the connectionto the SgNB 1 maintained. The malfunctions in the UE can be reduced.

Upon receipt of the additional SCG setting of the SgNB 2 in Step ST4217,the UE sets the MC not only to the MeNB and the SgNB 1 but also to theSgNB 2 according to the setting. In Step ST4218, the UE gives the MeNBthe RRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification including completionof the settings of the MC.

Upon recognizing that the UE has completed the settings of the MC, theMeNB notifies the SgNB 2 of the signaling indicating completion of theadditional SCG setting of the SgNB 2 in Step ST4219. The SgNB 2recognizes completion of the connection setting with the UE for the MC.

In Step ST4220, the UE starts the RA procedure with the SgNB 2. Thesetting for the RA procedure with the SgNB 2 is notified in the ASsetting from the SgNB 2 through Steps ST4216 and ST4217. The UE, whichhas been synchronized by the RA procedure, starts data communicationwith the SgNB 2 in Step ST4221.

The MeNB should have routing functions for a plurality of SgNBs. Sincethe number of the SgNBs to be connected in the DC is one, data splitinto the SgNB side has only to be transferred to one SgNB as it is.However, since the MeNB is connected to a plurality of the SgNBs in theMC, the MeNB needs to determine which SgNB the data split into the SgNBside is transferred to. Thus, the MeNB is provided with the routingfunctions of determining the SgNB to which data is transferred andtransferring the data to the determined SgNB.

The routing functions should include a function of transferring, to thePDCP of the MeNB, data received by its own MeNB from the UE and datareceived by a plurality of SgNBs and transferred to the MeNB.

The routing functions may be provided in the PDCP of the MeNB. Therouting functions may be provided as the lowest functions among thefunctions of the PDCP. Alternatively, the routing functions may beprovided separately from the PDCP. Although providing the routingfunctions separately from split functions is disclosed, the routingfunctions may be provided as a part of the split functions as analternative method. The functions may be not functions of splitting dataand then routing the data, but functions of splitting data between theMeNB and a plurality of SgNBs.

The routing functions may be performed for each data. The routing isperformed to the SgNBs for each data. Alternatively, the same routingmay be performed for a predetermined duration. Pieces of data for thepredetermined duration are routed to the same SgNB. This enablesflexible routing. The routing appropriate for a communication qualitystate of each SgNB is possible.

The same applies to the UE side.

In Step ST4222, the MeNB routes data into its own MeNB, and the SgNB 1and the SgNB 2 to which the MC has been set. Since the number ofsecondary base stations to be connected is two, data from the high-levelNW is processed by the PDCP of the MeNB, and then split into its ownMeNB and the SgNB to be transferred. The data split into the SgNB sideis routed to the SgNB 1 and the SgNB 2 with the routing functions, andthen transferred to the SgNB 1 and the SgNB 2.

The data received by the SgNB 1 and the SgNB 2 from the UE istransferred to the MeNB, and then transferred to the PDCP of the MeNBwith the routing functions together with the data received in its ownMeNB. The data transferred to the PDCP is processed by the PDCP, andthen transferred to the high-level NW.

This enables the MC using a plurality of SgNBs. The MeNB can set the MCto the UE using the plurality of SgNBs. The UE can perform the MCthrough connecting with the MeNB and the plurality of set SgNBs.

When the setting of the SgNBs is canceled, the SCG configurations of theSgNBs to which the MC has been set should be canceled one by one.

Setting or canceling the secondary base stations to which the MC is setone by one can set, to the UE, the SgNBs appropriate according to radiopropagation situations of the MeNB and the respective SgNBs. This canprovide the UE with high throughput.

Even upon occurrence of a failure in the additional setting of the SgNBsfor the MC on the way, setting or canceling the secondary base stationsto which the MC is set one by one enables execution of the MC using thesettings of the SgNBs while the successful settings of the SgNBs for theMC until then are maintained. The additional setting for the next SgNBcan be made again from the successful setting of the SgNBs for the MC.Even upon occurrence of a failure in the additional setting of theSgNBs, a robust and stable system can be built.

Another method for setting a plurality of SCGs for the MC is disclosed.The MeNB sets, to the UE, the SCGs for the MC. A radio bearer forperforming the MC is set in the setting of the SCGs. The setting shouldbe notified via the RRC signaling.

A plurality of SCGs are set. A plurality of SCGs for the MC are set witha one-time setting. The MeNB signals the UE for a plurality of SCGsettings. The signaling for the plurality of SCG settings may beprovided for the MC. This enables the MeNB to set a plurality of SCGs tothe UE.

When the DC is previously set, a plurality of SCG settings for the MCmay be set with the one-time setting after the previous DC setting isreleased. When the MC is previously set and is then performed using theSCGs of different SgNB s, a new MC setting should be made with theone-time setting after the previous MC setting is released.

The previous DC setting or the previous MC setting may be releasedseparately from the signaling for setting the plurality of the SCGsettings for the MC. As an alternative method, the previous DC settingor the previous MC setting may be released via the same signaling asthat for setting the plurality of the SCG settings for the MC. This canreduce the amount of signaling and the control latency.

For example, the RRCConnectionReconfiguration for setting the RRCconnection may be used as the RRC signaling. The signaling shouldinclude, for example, information on a plurality of SCGs to be set. Alist may be used as information on the plurality of SCGs. For example, alist of a plurality of SCGs to be set should be provided, which shouldinclude pieces of the configuration information of the SCGs as many asthe set SCGs. The pieces of the configuration information of the SCGsmay be set, for example, in the SCG-ConfigPartSCG previously described.

Identifiers may be provided to groups of the SCGs to be set. Identifiersmay be provided to groups of SgNBs to be set. For example, when aplurality of SCG settings for the MC are collectively canceled,inclusion of the identifier of the group of the SCGs which have beenassigned in the setting, into the signaling for canceling the SCGs canreduce the amount of information for the setting.

The UE may store the identifier of the group of the SCGs in associationwith the SCGs of the SgNBs included in the group of the SCGs. The UE maydiscard the stored records when a state with the base station goes intoidle state. The UE should maintain the stored records when a state withthe MeNB goes into connected and inactive state, a connected state, oran inactive state.

For example, when the additional setting of a plurality of SCGs for theMC is collectively made again after the setting for the MC is canceled,the identifier of the group of the SCGs that is previously set isincluded in the signaling for the additional setting. The UE canrecognize the SCG configurations of the SgNBs included in the group ofthe SCGs, from the identifier of the group of the SCGs that ispreviously notified from the MeNB. Consequently, the amount ofinformation for the additional setting can be reduced.

The SCG configuration and a bearer configuration for performing the MCmay be included as information on each of a plurality of SCGs to be setfor the MC. Examples of the bearer configuration include a beareridentifier, and an AS setting for the bearer. The bearer should be setin the method described above. Each of the SCGs may include SCGidentifier information as previously described. This enables the MeNB toset, to the UE, the SCG configurations of a plurality of SgNBs for theMC at one time.

FIGS. 19 and 20 illustrate an example sequence for setting the MC. FIGS.19 and 20 are connected across a location of a border BL 1920. FIGS. 19and 20 illustrate the use of the MeNB and two SgNBs (SgNB 1 and SgNB 2).FIGS. 19 and 20 illustrate the use of the MCG split bearer. FIGS. 19 and20 illustrate a method for setting the SCG of a plurality of SgNBs forthe MC at one time. Since the sequence illustrated in FIGS. 19 and 20includes the same steps as those of the sequence illustrated in FIGS. 17and 18 , the same step numbers are applied to the same Steps and thecommon description thereof is omitted.

In Step ST4301, the MeNB determines to perform the MC using a pluralityof SgNBs for the UE. Here, the MeNB determines to perform the MC usingthe SgNB 1 and the SgNB 2. In Steps ST4203 and ST4215, the MeNB notifiesthe SgNB 1 and the SgNB 2, respectively, of SgNB addition requests. InSteps ST4204 and ST4216, the SgNB 1 and the SgNB 2, respectively, notifythe MeNB of the AS settings determined in response to the additionrequests.

In Step ST4302, the MeNB notifies the UE of the settings of the MC. TheMeNB notifies, as the settings of the MC, the SCG configurations of theplurality of SgNBs for the MC, and the bearer configuration forperforming the MC. The RRCConnectionReconfiguration for setting the RRCconnection may be used as the signaling.

In Step ST4302, the MeNB may notify the UE of release of the settings aswell when the DC or the MC is previously set. The notification enablesthe collective SCG settings of the plurality of SgNBs for the MC. The UEcan clearly recognize the settings for connection to the SgNB 1 and theSgNB 2 for the MC. The malfunctions in the UE can be reduced.

Upon receipt of the additional SCG settings of the SgNB 1 and the SgNB 2in Step ST4302, the UE sets the MC to the MeNB, the SgNB 1, and the SgNB2 according to the settings. In Step ST4303, the UE gives the MeNB theRRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification including completionof the settings of the MC.

Upon recognizing that the UE has completed the settings of the MC, theMeNB notifies the SgNB 1 of the signaling indicating the completion ofthe additional SCG setting of each of the SgNBs in Step ST4207, andnotifies the SgNB 2 of the signaling indicating the completion of theadditional SCG setting of each of the SgNBs in Step ST4219. The SgNB 1and the SgNB 2 recognize completion of the connection settings with theUE for the MC.

In Steps ST4208 and ST4220, the UE starts the RA procedures with theSgNB 1 and the SgNB 2, respectively. The setting for the RA procedure ofthe SgNB 1 is notified in the AS setting from the SgNB 1 through StepsST4204 and ST4302. The setting for the RA procedure with the SgNB 2 isnotified in the AS settings from the SgNB 2 through Steps ST4216 andST4302. The UE, which has been synchronized by the RA procedure, startsdata communication with the SgNB 1 and the SgNB 2 in Steps ST4209 andST4221, respectively.

Since Steps ST4222 to ST4226 are the same processes as those in FIGS. 17and 18 , the description thereof is omitted.

This enables the MC using a plurality of SgNBs. The MeNB can set the MCusing the plurality of SgNBs to the UE. The UE can perform the MCthrough connecting with the MeNB and the plurality of set SgNBs.

When the SCG settings of the plurality of SgNBs is canceled, all the SCGconfigurations of the SgNBs to which the MC has been set arecollectively canceled. The signaling from the MeNB to the UE at one timecancels the SCG settings of the plurality of SgNBs.

As such, setting or canceling the secondary base stations to which theMC is set at one time enables reduction in the amount of signaling.Moreover, the setting or canceling of the MC can be controlled with lowlatency. Thus, an appropriate SgNB can be set to the UE according to thefast time variation in the radio propagation situations of the MeNB andthe SgNBs. This can provide the UE with high throughput.

As methods for setting or canceling a plurality of SCGs for the MC, themethod for setting or canceling the SCGs one by one, and the method forsetting or canceling the plurality of SCGs for the MC with the one-timesetting are disclosed. These methods may be appropriately combined. Forexample, a plurality of SCGs may be set instead of setting the SCGs oneby one. A plurality of SCGs are set to the same bearer. The method forsetting the plurality of SCGs for the MC with the one-time setting maybe applied to a method for setting the plurality of SCGs.

Information indicating whether or not the setting is the additional SCGsetting while the previous SCG setting is maintained may be included.The UE can recognize that the setting of a plurality of SCGs for the MCthat has been made with the one-time setting is the additional SCGsetting that maintains the previous SCG setting.

In such a case, information for canceling the setting for the MC may beseparately provided from information for canceling settings of one ormore SCGs. The information for canceling the setting for the MC may beinformation for canceling the current bearer format. Such informationmay be used, for example, for canceling the MCG split bearer. Theinformation for canceling settings of one or more SCGs may beinformation for canceling the settings of one or more SCGs from the MC,that is, information for eliminating an SCG from the SCGs of the SgNBsperforming the MC. The SCG may be identified using an identifier of theSCG.

The MeNB should appropriately use the information according to asituation. The MeNB sets the information to the UE according to whetherthe setting for the MC or the settings of one or more SCGs are canceled.Upon receipt of the information, the UE can determine whether thesetting for the MC or the settings of one or more SCGs are canceled.

For example, when notified of the cancelation of the setting for the MCwith a plurality of SCGs being set, the UE cancels all the settings ofthe SCGs to cancel the setting for the MC. The UE cancels the bearerformat to which the MC has been set. For example, when notified of thecancelation of the settings of one or more SCGs with a plurality of SCGsset, the UE cancels the settings of the SCGs. However, the UE does notcancel the setting for the MC. The UE does not cancel the bearer formatin which the MC has been set. The UE continues the MC using the rest ofthe SCGs.

Consequently, the SCGs for the MC can be flexibly set. The MC can beflexibly set using appropriate SgNBs according to a state such as amoving speed of the UE and a service to be provided, a position of thebase station, change in the radio propagation environment between the UEand the base station, and other conditions. The throughput can beincreased.

Another method for setting a plurality of SCGs for the MC is disclosed.The MeNB sets a radio bearer for performing the MC to the UE. The MeNBsets the SCGs for the MC in the setting of the radio bearer. The MeNBshould notify the setting via the RRC signaling.

The MeNB sets, to the UE, the SCGs of one or more SgNBs for a radiobearer for performing the MC. Since the SCGs of many SgNBs can be set toone or more bearers at one time when the number of secondary basestations that can be connected to the UEs for the MC is large, theamount of signaling can be reduced.

For example, the RRCConnectionReconfiguration for setting the RRCconnection may be used as the RRC signaling. For example, the signalingshould include information on one or more radio bearers to which the MCis set. A list may be used as information on the one or more radiobearers. For example, a list of the one or more radio bearers to whichthe MC is set should be provided to include, in the list, SCGconfigurations corresponding to the radio bearers and bearerconfigurations corresponding to the SCGs as many as the number of theradio bearers to which the MC is set. Information on the SCGconfigurations of the radio bearers and the bearer configurations may beset, for example, in the SCG-ConfigPartSCG previously described.

Identifiers of the radio bearers may be included as information on theone or more radio bearers to be set in a list. Here, theSCG-ConfigPartSCG may be prevented from including the identifiers of theradio bearers. Alternatively, the identifiers of the radio bearers neednot be included as the information on the one or more radio bearers tobe set in a list. Here, the identifiers of the radio bearers should beincluded in the SCG-ConfigPartSCG. Assigning the identifiers of theradio bearers can facilitate the settings of the radio bearers forperforming the MC.

SCG identifiers with the same bearer configuration may be included asthe bearer configuration information for each of the SCGs. When the SCGidentifiers are included as the bearer configuration informationnotified from the MeNB, the UE can determine that the same configurationas the bearer configuration of the SCGs with the SCG identifiers isapplied. When a part of the bearer configuration is different, the SCGidentifier and information on only the different bearer configurationmay be included as the bearer configuration information. The sameinformation as the bearer configuration information on the SCGidentifiers may be applied as information on the bearer configurationthat is not included as information.

Since the entirety of the bearer configuration information need not beincluded as the bearer configuration information for each of the SCGs tobe notified from the MeNB to the UE, the amount of information necessaryfor signaling can be reduced.

In the previous example, the SCG configuration information and thebearer configuration information of each radio bearer to which the MC isset are set in the SCG-ConfigPartSCG . As an alternative method, the SCGconfiguration information and the bearer configuration information maybe separately set. For example, the bearer configuration information inthe SCG-ConfigPartSCG is set separately from the SCG-ConfigPartSCG. Thepieces of the bearer configuration information of the one or more radiobearers may be set in a list. The SCG configuration information is setin the SCG-ConfigPartSCG.

This method may be used when the SCGs of all the SgNBs to which the MCis set have the same bear setting. This can omit the setting of thebearer configuration information to each of the SCGs, and reduce theamount of information necessary for the signaling.

The MeNB sets the radio bearer for performing the MC to the UE. Theaforementioned sequence is applicable to a sequence for setting the SCGsfor the MC in the settings of the radio bearer. For example, in StepST4302 of the sequence illustrated in FIGS. 19 and 20 , the MeNB givesthe UE a notification including information on the one or more radiobearers to which the MC is set, as a replacement for the SCG settings ofone or more SgNBs to which the MC is set.

For example, a list of one or more radio bearers to which the MC is setis provided as one or more pieces of radio bearer information toinclude, in the list, SCG configurations corresponding to the radiobearers and bearer configurations corresponding to the SCGs as many asthe number of the radio bearers to which the MC is set. Information onthe SCG configurations of the radio bearers and the bearerconfigurations may be set, for example, in the SCG-ConfigPartSCGpreviously described. Here, information on the SCG configurations andthe bearer configurations of the SgNBs 1 and 2 is set.

Upon receipt of the one or more pieces of radio bearer information inStep ST4302, the UE sets the MC to the MeNB, the SgNB 1, and the SgNB 2according to the settings. In Step ST4303, the UE gives the MeNB the RRCconnection reconfiguration complete(RRCConnectionReconfigurationComplete) notification including completionof the settings of the MC.

Since such a method enables the SCGs of many SgNBs to be set at one timeto one or more bearers, the amount of signaling can be reduced. With thesetting at one time, the MC can be controlled with low latency. Thesetting for each bearer requires only the setting of a target bearer tobe changed or modified when the bearer format is changed or modified foreach bearer, which can avoid complexity in the control. For example, theamount of processing in the UE can be reduced.

When data is communicated between the MeNB and each of the SgNB s, anSgNB identifier may be assigned to the data. Also, each of the SgNBsshould notify the MeNB of a downlink data transmission state from itsown SgNB to the UE. For example, each of the SgNBs notifies the highestPDCP PDU SN at which transmission to the UE has been successful, amongthe PDCP PDUs transferred from the MeNB. For example, each of the SgNBsnotifies the buffer volume of its own SgNB for the bearer to which theMC is set. The SgNB may notify the amount of data required forsatisfying the QoS set as the buffer volume. The SgNB may notifyinformation for each bearer to which the MC is set.

For example, each of the SgNBs notifies the buffer volume of its ownSgNB for the UE to which the MC is set. The buffer volume to be notifiedmay be the minimal amount of data required. For example, each of theSgNBs notifies information on a packet lost by its own SgNB among piecesof data transferred from the MeNB. An identifier of each of the SgNBsmay be assigned to the downlink data transmission state from its ownSgNB to the UE which is to be notified from the SgNB to the MeNB.

Assigning the identifier of each of the SgNBs enables the SgNB to checkwhether the notification is given to its own SgNB, and enables the MeNBto identify which SgNB the notification has been received from. The MeNBshould determine, for example, whether to set, modify, change, or cancelthe SgNB for the MC, using the downlink data transmission state fromeach of the SgNBs. The MeNB may determine which SgNB a packet is routedto, using the downlink data transmission state from each of the SgNBs.The setting of the MC or the routing according to a data transmissionstate between each of the SgNBs and the UE is possible.

A data split method with the MC in the uplink is disclosed. The MeNBassigns a plurality of thresholds for transmission to the SgNBs, andnotifies the UE of the plurality of thresholds. Since a plurality ofSgNBs for the MC are set in the MC, not limited to a single thresholdbut a plurality of thresholds are set according to the number of SgNBsto be set.

For example, thresholds should be assigned as many as the number ofSgNBs to be set for the MC. Alternatively, groups each consisting of oneor more SgNBs may be formed, and thresholds may be assigned as many asthe number of the SgNB groups. The MeNB assigns the plurality ofthresholds and notifies the UE of the thresholds. The MeNB may give thenotification via the RRC signaling.

For example, when three SgNBs are set for the MC, the MeNB assigns threethresholds and notifies the UE of the thresholds. The thresholds aredenoted as TH1, TH2, and TH3. When the buffer volume of the uplink dataof the UE is smaller than or equal to TH1, the UE performs uplinktransmission only to the MeNB. When the buffer volume of the uplink dataof the UE is larger than TH1 and smaller than or equal to TH2, the UEperforms uplink transmission to the MeNB and one of the SgNBs. When thebuffer volume of the uplink data of the UE is larger than TH2 andsmaller than or equal to TH3, the UE performs uplink transmission to theMeNB and two of the SgNBs. When the buffer volume of the uplink data ofthe UE is larger than TH3, the UE performs uplink transmission to theMeNB and the three SgNBs.

As such, gradually increasing or decreasing the number of the SgNBs tobe used for the uplink transmission can prevent, when the amount ofuplink data is less, the UE from transmitting the data to many SgNBs.This can suppress increase in the power consumption of the UE.

A method for setting a plurality of thresholds may be setting onethreshold, and then setting, as the other thresholds, values obtained bymultiplying the set threshold by predetermined numbers. For example,only TH1 is set, and TH2=TH1×2 and TH3=TH1×3 are calculated. As anotherexample, TH2=TH1×1.5 and TH3=TH1×2 may be available. The predeterminednumbers may be determined in advance in, for example, a specification.Alternatively, the predetermined numbers may be semi-statically notifiedto the UE via the RRC signaling. This can reduce the amount of signalingto be notified to the UE.

The MeNB may set, to the UE, which SgNB the uplink transmission isperformed to when the buffer volume of the uplink data exceeds athreshold. For example, priorities may be assigned to the use orders ofthe SgNBs. The MeNB notifies the UE of the priorities. For example, whenthree SgNBs are set for the MC, the SgNB 1, the SgNB 2, and the SgNB 3are set in descending order of the priorities. The MeNB may notify theUE of the identifiers of the respective SgNB s and the priorities inassociation with one another.

When the buffer volume of the uplink data of the UE is smaller than orequal to TH1, the UE performs uplink transmission only to the MeNB. Whenthe buffer volume of the uplink data of the UE is larger than TH1 andsmaller than or equal to TH2, the UE performs uplink transmission to theMeNB and the SgNB 1. When the buffer volume of the uplink data of the UEis larger than TH2 and smaller than or equal to TH3, the UE performsuplink transmission to the MeNB, the SgNB 1, and the SgNB 2. When thebuffer volume of the uplink data of the UE is larger than TH3, the UEperforms uplink transmission to the MeNB, the SgNB 1, the SgNB 2, andthe SgNB 3.

The MeNB may notify the priorities together with a threshold.Alternatively, the MeNB may notify the priorities separately from thethreshold. The priorities of the SgNB s may be changed. Changing thepriorities of the SgNBs according to a communication state between eachof the SgNBs and the UE can increase the throughput of the uplinkcommunication.

The previous example discloses that the UE performs uplink transmissionfirst to the MeNB when the buffer volume of the uplink data of the UE issmaller than or equal to a predetermined threshold. As another example,the UE may perform the transmission to an SgNB when the buffer volume ofthe uplink data of the UE is smaller than or equal to the predeterminedthreshold, and perform the transmission to the MeNB when the buffervolume of the uplink data of the UE is larger than the threshold. TheMeNB may set, to the UE, which one of the MeNB and the SgNBs the uplinktransmission is performed to when the buffer volume of the uplink datais smaller than or equal to a threshold and exceeds the threshold. Thepriorities may be assigned including the MeNB, and notified to the UE.Using the SgNBs at an early stage increases the throughput of the uplinkdata.

When the MC using a plurality of SgNBs is set to the MeNB, the UE mayroute data from the upper layer between the MeNB and all the SgNBs. Theprevious method should be appropriately applied to the routingfunctions. Alternatively, with application of the data split method inthe uplink, routing may be performed between the use MeNB and the useSgNBs. The SgNBs into which data is split can be flexibly set.

A method for starting transmission of the uplink data from the UE to thebase station side is disclosed. The UE notifies the base station side ofa scheduling request (SR). The UE may notify the base station side of aBuffer Status Report (BSR).

The UE notifies the SgNB that performs uplink transmission of the SR orthe BSR. Consequently, the SR or the BSR can be processed in a lowerlayer in each of the SgNBs.

As an alternative method, the UE may notify the MeNB of the SR or theBSR addressed to the SgNB that performs uplink transmission. Thenotification should include information indicating which SgNB the SR orthe BSR is addressed to. The information may be an SgNB identifier. Uponreceipt of the SR or the BSR addressed from the UE to the SgNB, the MeNBnotifies the SgNB to which the SR or the BSR is addressed of informationindicating the reception of the SR or the BSR and information indicatingdetails of the SR or the BSR. Upon receipt of these pieces ofinformation, the SgNB performs uplink scheduling for the UE according tothe details.

This enables the MeNB to perform the uplink scheduling for the UE tocorrespond to the SR or the BSR addressed to each of the SgNBs.

As an alternative method, the UE may notify the MeNB of the SR or theBSR as uplink transmission of a bearer to which the MC is set. The UEnotifies not each of the SgNBs but the MeNB of the SR or the BSR as theuplink transmission of the bearer to which the MC is set. Upon receiptof the notification, the MeNB determines which SgNB is made to performuplink scheduling using the assigned threshold. The MeNB should notifythe SgNB which is made to perform the uplink scheduling of a request forstarting the uplink scheduling.

The MeNB may notify the SgNB of the details of the SR or the BSR thathave been notified from the UE. Alternatively, the MeNB may compute thedata capacity required for the SgNB to perform the uplink scheduling tonotify the SgNB of a result of the computation. The UE need not notifythe SR or the BSR for each SgNB. The UE should notify the MeNB of the SRor the BSR as the uplink transmission of the bearer to which the MC isset. Thus, the power consumption of the UE can be reduced.

The eNBs that are base stations in the LTE may be used as secondary basestations for the MC. The secondary base stations may include an eNB anda gNB. The method disclosed in the sixth embodiment should beappropriately applied thereto. Since the secondary base stations do notuse the New AS sublayer in the sixth embodiment, the eNBs can be used asthe secondary base stations.

The method disclosed in the sixth embodiment can configure theconnection of one UE to one master base station and a plurality ofsecondary base stations. This can increase the throughput ofcommunication to be provided for the UE. Moreover, the connection to aplurality of base stations can enhance the reliability.

The First Modification of the Sixth Embodiment

In 3GPP, setting a New AS sublayer protocol as a protocol in NR has beenproposed (see Non-Patent Document 9 (TR38.804 V.14.0.0)). The New ASsublayer protocol is also referred to as a Service Data AdaptationProtocol (SDAP). This Description may denote the New AS sublayer as aNew AS layer. In the New AS sublayer, PDU session data is mapped to aDRB.

The following has been proposed as a QoS architecture in an NG-CN andNR. One PDU session can be mapped to one or more DRBs. A different PDUsession is mapped to a different DRB. A plurality of QoS flows areconfigured for one PDU session. One or more QoS flows can be mapped toone DRB.

A high-level device puts a QoS marker to PDU session data according tothe QoS. The use of a QoS flow identifier as a QoS marker has beenproposed. The gNB establishes a DRB according to the QoS of the PDUsession data to map the PDU session data to the DRB and vice versaaccording to the QoS flow identifier in the New AS sublayer.

FIG. 21 illustrates an architecture and a dataflow when the high-levelNW is an NG-CN and the base station is a gNB in NR. In 3GPP, the 5G corenetwork is referred to as a “Next Generation Core Network” (abbreviatedas “NG-CN”). The NG-CN includes an Access & Mobility management Function(AMF), a Session Management Function (SMF), and a User Plane Function(UPF) of the User Plane (U-Plane).

The AMF and the gNB are connected through the N2 interface. The UPF andthe SMF are connected through the N3 interface. The SMF and the UPF areconnected through the N4 interface. The AMF and the SMF may be connectedthrough the N11 interface.

The gNB includes the New AS layers as well as the PDCPs, the RLCs, theMAC, and the PHY. The New AS layer of the gNB is connected to thehigh-level NW for each PDU session. FIG. 21 illustrates cases where oneDRB is configured for one PDU session and two DRBs are configured forone PDU session.

FIG. 21 exemplifies association between QoS flows when the two DRBs areconfigured for the one PDU session. In FIG. 21 , three QoS flows,namely, a QoS flow 1, a QoS flow 2, and a QoS flow 3 are present for theone PDU session. The gNB sets the DRB 1 to the QoS flow 1 and the QoSflow 2, and maps the QoS flow 1 and the QoS flow 2 to the DRB 1 in theNew AS layer. The gNB sets the DRB 2 to the QoS flow 3, and maps the QoSflow 3 to the DRB 2 in the New AS layer.

In the gNB, data of the QoS flow 1 and the QoS flow 2 is processed withthe setting of the DRB 1, and data of the QoS flow 3 is processed withthe setting of the DRB 2.

The DC in the presence of the New AS sublayer protocol has beendiscussed (see “10.2.2 MR-DC with 5GC” in Non-Patent Document 28(TS37.340 V0.2.0 (2017-06)). However, the details of the MC in thepresence of the New AS sublayer protocol have not yet been discussed.The first modification of the sixth embodiment discloses a method forperforming the MC in the presence of the New AS sublayer protocol. Themethod with the MCG split bearer is described.

FIG. 22 illustrates an architecture of the MC. FIG. 22 illustrates thatthe high-level NW is an NG-CN, the master base station is a base stationin NR (gNB), and the secondary base stations are base stations in NR(gNBs). The master base station in NR is referred to as the MgNB, andthe secondary base stations in NR are referred to as the SgNBs. Theprotocol configuration of the gNB includes the New AS sublayer, thePDCP, the RLCs, the MAC, and the PHY. The New AS sublayer is set higherthan the PDCP.

Although the master base station is the gNB in NR in FIG. 22 , themaster base station may be an eNB obtained by adding the New AS sublayerto a base station in the LTE.

Although FIG. 22 illustrates the architecture on the base station side,the architecture on the UE side is identical to that on the base stationside except for the high-level NW. One UE includes the RLC, the MAC, andthe PHY for the MgNB, the RLC, the MAC, and the PHY for each of SgNBsset for the MC, the New AS sublayer, and the PDCP.

FIG. 22 illustrates the use of the MCG split bearer. The high-level NWis connected to the MgNB, and the SgNBs for the MC are connected to theMgNB. The New AS sublayers of the MgNB map downlink data to a DRBaccording to a QoS flow identifier. The PDCP processes the downlink datafor each of the mapped DRBs. Even when the number of SgNBs is more thanone, the PDCP assigns one serial sequence number (SN) to each data. Thedata to which the SN is assigned is split into the MgNB and the SgNBs.The pieces of split data are transmitted to the RLC in each of the MgNBand the SgNBs, processed by the RLC, the MAC, and the PHY in each of theMgNB and the SgNBs, and transmitted to the UE.

The pieces of data received by the UE from the MgNB and the SgNBs areprocessed by the PHYs, the MACs, and the RLCs for the MgNB and theSgNBs, and then transferred to the PDCP. The PDCP performs reorderingbased on the SNs assigned to the pieces of the data transferred fromlayers for the MgNB and the SgNBs, and transfers the pieces of data tothe New AS sublayer. The New AS sublayer separates the data into the QoSflows according to the QoS flow identifiers, and transfers the pieces ofdata to the upper layer.

In the UE, the New AS sublayer maps, as the uplink data, the pieces ofdata from the upper layer to DRBs according to the QoS flow identifiers.Then, the PDCP processes the pieces of data for each of the mapped DRBs.Similarly in the downlink, even when the number of SgNBs is more thanone, the PDCP assigns one serial sequence number (SN) to each data inthe uplink. The data to which the SN is assigned is split into the RLCsfor the MgNB and the SgNBs to be transferred. The pieces of thetransferred data are processed by the RLCs, the MACs, and the PHYs forthe MgNB and the SgNBs, and then transmitted to the MgNB and the SgNBs.

The pieces of data received from the UE by the MgNB and the SgNBs areprocessed by the PHYs, the MACs, and the RLCs for the MgNB and theSgNBs, and then transferred to the PDCP of the MgNB. The PDCP of theMgNB performs reordering based on the SNs assigned to the pieces ofdata, and transfers the pieces of data to the New AS sublayer. The NewAS sublayer separates the pieces of data into the QoS flows according tothe QoS flow identifiers, and transfers the pieces of data to thehigh-level NW.

A method for setting the MC is disclosed. The MC is set for each DRB.The MC is set with the MCG split bearer for each DRB.

FIG. 23 is a conceptual diagram illustrating a dataflow when the MC isset for each DRB. Assume a DRB to which the MC is set as the DRB 1.Assume QoS flows to be mapped to the DRB 1 as the QoS flow 1 and the QoSflow 2. The MC is performed on the DRB 1 with the MCG split bearer,using the MgNB, the SgNB 1, the SgNB 2, and the SgNB 3.

The PDCP splits and routes data of the QoS flow 1 and the QoS flow 2that are mapped to the DRB 1, to the MgNB and the SgNBs. Similarly inthe downlink, the PDCP splits and routes the data of the QoS flow 1 andthe QoS flow 2 that are mapped to the DRB 1 by the UE, into the RLCs forthe MgNB and the SgNBs as the uplink data.

Not the DRB 1 set in the downlink but a default DRB may be used in theuplink. In such a case, the PDCP should split and route the data of theQoS flow 1 and the QoS flow 2 for which the UE uses the default DRB, tothe RLCs for the MgNB and the SgNBs.

In the MgNB, the PDCP reorders the pieces of data from the MgNB and theSgNBs using the SNs. The New AS layer separates the pieces of data foreach of the QoS flows using the QoS flow identifiers, and transfers thepieces of separated data to the high-level NW.

Setting the MC for each DRB enables the settings of the MC withoutchanging a mapping relationship between the DRBs and the QoS flows whichis set without performing the MC. This can avoid complexity in thecontrol over the MC.

The sequence disclosed in the sixth embodiment is applicable to asequence when the MC is set for each DRB. For example, the MeNB maynotify each of the SgNBs to which the MC is set of QoS flowcharacteristics information, in the SgNB addition requests in StepsST4203 and ST4215 of the sequence illustrated in FIGS. 19 and 20 .

Six examples of the QoS flow characteristics information are disclosedbelow:

(1) a bearer identifier;

(2) a bearer configuration;

(3) QoS flow identifiers;

(4) a QoS profile of each QoS flow;

(5) a PDU session identifier; and

(6) combinations of (1) to (5) above.

The MgNB may notify each of the SgNBs to which the MC is set of a QoSprofile of each QoS flow to be requested from the SgNB. The MgNB maydetermine a QoS profile setting for each of the SgNBs to which the MC isset to satisfy the QoS profile of the QoS flow on which the MC isperformed.

The MgNB may notify each of the SgNBs to which the MC is set of thebearer configuration to be requested from the SgNB. The MgNB may set thebearer configuration identical to that of its own MgNB. Alternatively,the MgNB may determine bearer configurations so that the bearerconfiguration of its own MgNB and the bearer configuration of the SgNBsto which the MC is set satisfy the QoS profile of the QoS flow on whichthe MC is performed.

Upon receipt of the SgNB addition request from the MgNB, the SgNBdetermines the AS setting of the bearer to which the MC is set, usingthe QoS flow characteristics information included in the additionrequest. Each of the SgNBs notifies the MgNB of the determined ASsetting.

Consequently, the MgNB can set the MC to the UE for each DRB when theNew AS sublayer is necessary. Thus, the MC for each bearer can beperformed, with the MCG split bearer, between the MgNB and the UE andbetween each of the SgNBs and the UE.

The method disclosed in the sixth embodiment should be appropriatelyapplied to a data split method with the MC in the uplink.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The SR or the BSR for each QoS flow maybe provided and notified from the UE to the base station side.

Another method for setting the MC is disclosed. The MC is set for eachQoS flow. The MC with the MCG split bearer is performed on one or moreof the QoS flows to be mapped to the DRB s by the New AS sublayer.

FIG. 24 is a conceptual diagram illustrating a dataflow when the MC isset for each QoS flow. Assume the QoS flow on which the MC is performedas the QoS flow 1. The MgNB splits and routes only the QoS flow 1 in theDRB 1.

A method for identifying data to be split is disclosed. The MgNBdetermines whether to split data according to a QoS flow identifierassigned to the data. Similarly, the UE determines whether to splituplink data according to a QoS flow identifier assigned to the data.

For example, when data from the PDCP includes an identifier of the QoSflow 1 in the MgNB, the MgNB determines to split the data into theSgNBs, and splits and routes the data into the SgNBs. The same appliesto the uplink data. When data from the PDCP includes the identifier ofthe QoS flow 1 in the UE, the UE determines to split the data into theRLCs for the SgNBs, and splits and routes the data into the RLCs of theSgNBs.

This enables the MC with the MCG split bearer for each QoS flow.

Information indicating whether to split data may be separately providedas an alternative method. The New AS layer may add the information todata from the high-level NW or the upper layer. Alternatively, the PDCPlayer may add the information. A QoS flow identifier may be used.Information indicating that data is split is added to data with a QoSflow identifier which is to be split. Information indicating that datais not split is added to data with a QoS flow identifier which is not tobe split.

Only information indicating whether or not to split data may be added tothe data. Consequently, the split or routing functions can determinedata to be split and routed, using the information which is added to thedata and indicates whether or not to split data.

By adding the information indicating whether or not to split data by theNew AS layer or the PDCP layer in the MgNB or the UE, the informationindicating whether or not to split data can be used as information to beused in the RAN. Consequently, the split or routing functions need notread the QoS flow identifier assigned by the high-level NW or the upperlayer. This can simplify the processing.

The sequence when the MC is set for each DRB is applicable to a sequencewhen the MC is set for each QoS flow. The MgNB needs to notify the UE toset the MC for each QoS flow. Thus, the MgNB notifies the QoS flow towhich the MC is set in Step ST4302 of the sequence illustrated in FIGS.19 and 20 . The MgNB should notify the QoS flow identifier for settingthe MC. Similarly, the MgNB should notify the UE of the SCGconfiguration and the bearer configuration.

Consequently, the MgNB can set the MC to the UE for each QoS flow. Thus,the MC for each QoS flow can be performed, with the MCG split bearer,between the MgNB and the UE and between each of the SgNBs and the UE.

Another method for performing the MC for each QoS flow is disclosed. ADRB for the QoS flow on which the MC is performed is additionally set.The QoS flow on which the MC is performed is mapped to the additionallyset DRB. Through setting the MC to the additionally set DRB, the MC canbe set to the QoS flow mapped to the DRB.

FIG. 25 is a conceptual diagram illustrating a dataflow in additionallysetting a DRB to which the QoS flow, on which the MC is performed, ismapped. Assume the QoS flow on which the MC is performed as the QoS flow1.

Assume that the mapping relationship between the QoS flows and the DRBsbefore the MC is set is the same one illustrated in FIG. 21 . Before theMC is set, the QoS flow 1 and the QoS flow 2 are mapped to the DRB 1.

As illustrated in FIG. 25 , the MgNB additionally sets a DRB X1 formapping the

QoS flow 1 to set the QoS flow 1 to the MC. The New AS sublayer maps theQoS flow 1 to the DRB X1. The New AS sublayer maps the QoS flow 2 to theDRB 1 similarly before the MC is set.

Consequently, the QoS flow on which the MC is performed can be mapped tothe DRB X1. The MgNB sets the MC to the DRB X1. Consequently, the MC isperformed on the QoS flow 1 to be mapped to the DRB X1. The MgNB shouldsplit and route data of the QoS flow 1 to perform the MC with the MCGsplit bearer.

The DRB configuration to be added should be set using the QoS profile ofthe QoS flow to be split. The QoS profile of the QoS flow to be notifiedfrom the high-level NW may be used. The MgNB additionally sets the DRBX1, and the New AS sublayer maps the data of the QoS flow 1 to the DRBX1. The New AS sublayer determines which DRB data is mapped to,according to the QoS flow identifier which the high-level NW assigns tothe data.

The MgNB sets the DRB X1 to the MC using the MCG split bearer, splitsdata of the QoS flow 1 into the SgNB side to be used for the MC, androutes the data into the SgNB 1, the SgNB 2, and the SgNB 3.

The MgNB should notify the UE of the configuration of the DRB X1additionally set for the MC. For example, the method for notifying theconfiguration of the DRB for performing the MC from the MgNB to the UE,which is disclosed in the sixth embodiment, should be applied to thisnotification.

The MgNB should notify the UE of the mapping relationship between theQoS flows and the DRBs in the New AS layer. The MgNB should associate,for example, identifiers of the DRBs and the configuration informationon the DRBs with identifiers of the QoS flows and QoS profiles, andnotify them. Here, the MgNB notifies information indicating a mappingrelationship with the QoS flow 1 to be mapped to the DRB X1. Thisenables the UE to map the QoS flow 1 to the DRB X1 in the New ASsublayer.

Consequently, the UE can additionally set the DRB corresponding to theQoS flow on which the MC is performed, and set the MC to the DRB andperform the MC on the DRB. The same applies to the uplink data.

The New AS sublayer maps data of the QoS flow 2 to the DRB 1. Theconfiguration of the DRB 1 need not be changed. Since the configurationof the DRB 1 supports the QoS flow 2 before the MC is set, it cansupport the QoS flow 2 without any change. Since the MC is not set tothe DRB 1, the MC is not performed on the data of the QoS flow 2. Thus,communication is performed using only the MgNB.

The MgNB may notify the UE of information on the QoS flow to be mappedto the DRB 1. With the additional setting of the DRB X1, the QoS flow tobe mapped to the DRB 1 is changed from the QoS flow 1 and the QoS flow 2before the MC is set, into the QoS flow 2. A notification of change orreconfiguration of the QoS flow from the MgNB to the UE enables the UEto recognize the QoS flow to be mapped to the DRB 1.

The RRC signaling should be used for notifying the change orreconfiguration of the QoS flow to be mapped to the DRB. Thenotification may be given via the same signaling as that foradditionally setting the DRB X1.

The MgNB may reconfigure the DRB 1. The MgNB should reconfigure the DRB1 so that, for example, the DRB 1 has a DRB configuration appropriatefor the QoS flow 2 to be mapped to the DRB 1 after the MC is set. TheMgNB should set the DRB 1 using the QoS profile of the QoS flow 2. TheMgNB reconfigures the DRB 1, and the New AS sublayer maps the data ofthe QoS flow 2 to the DRB 1.

The MgNB should notify the UE of the configuration of the reconfiguredDRB 1. For example, the method for notifying the configuration of theDRB from the MgNB to the UE, which is disclosed in the sixth embodiment,should be applied to this notification. The UE can reconfigure theconfiguration of the DRB 1. The same applies to the uplink data.Consequently, the DRB configuration appropriate for change in the QoSflow to be mapped is possible.

The aforementioned additional setting and removal of the DRB may beapplied to a method for reconfiguring the DRB to which the QoS flow ismapped. Consequently, the DRB configuration appropriate for change inthe QoS flow to be mapped is possible.

FIGS. 26 and 27 illustrate an example sequence for setting the MC foreach QoS flow. FIGS. 26 and 27 are connected across a location of aborder BL 2627. FIGS. 26 and 27 illustrate that the MgNB additionallysets the DRB including the QoS flow on which the MC is performed. InStep ST4901, data is communicated between the UE and the MgNB. In StepST4902, the MgNB determines to perform the MC for each QoS flow for theUE. In Step ST4903, the MgNB determines to additionally set the DRB towhich the QoS flow on which the MC is performed is mapped. In StepST4904, the MgNB determines and adds the configuration of the DRB forthe QoS flow on which the MC is performed.

In Step ST4905, the MgNB notifies the UE of the added DRB configurationand the QoS flow identifier to be mapped to the added DRB. The MgNB maynotify a QoS profile of the QoS flow. The MgNB may also notify aninstruction for aborting transmission of new data of the QoS flow withthe DRB to which the QoS flow has been mapped before the additionalsetting. The MgNB should give the instruction via the RRC signaling. Forexample, these pieces of information may be included in the RRCconnection reconfiguration to be notified.

The UE makes a setting using information received from the MgNB, andnotifies the MgNB of completion of the setting in Step ST4906. The UEmay notify the completion of the setting via the signaling for the RRCconnection reconfiguration complete notification.

In Step ST4907, the UE aborts transmission of new data of the QoS flowwith the DRB to which the QoS flow has been mapped before the additionalsetting. The UE also makes the additional setting using the DRBconfiguration notified from the MgNB, maps, to the additional DRB, theQoS flow to be mapped to the additional DRB, and starts transmittingdata. In Step ST4908, the MgNB maps, to the additional DRB, the QoS flowto be mapped to the additional DRB and starts transmitting data.

The DRB before the additional setting is still maintained even if thereis no QoS to be mapped. With the DRB before the additional settingmaintained, data can be processed before aborting transmission of thedata. For example, a retransmission process, etc., in a lower layer ispossible. The UE should insert a marker at the end of data to betransmitted with the DRB before the additional setting. The UE may lasttransmit data corresponding to the marker. This marker is referred to asan end marker.

In Step ST4909, data of the QoS flow is communicated between the UE andthe MgNB with the DRB additional set. In Step ST4909, the data of theQoS flow is also communicated with the DRB before the additionalsetting. In Step ST4910, the MgNB determines whether or not the dataprocessing with the DRB before the additional setting has beencompleted. The MgNB should make the determination using the end marker.When the data processing is not completed, the MgNB returns to StepST4909 to perform the data processing. When the data processing iscompleted, the DRB setting before the additional setting is canceled inStep ST4911.

In Step ST4912, the MgNB notifies the UE to cancel the DRB settingbefore the additional setting. The MgNB should notify the cancellationvia the RRC signaling. For example, the cancellation should be includedin the RRC connection reconfiguration to be notified. Upon receipt ofthe cancellation of the DRB setting before the additional setting, theUE cancels the DRB setting before the additional setting.

The MgNB may insert an end marker at the end of data to be transmittedwith the DRB before the additional setting. The UE may cancel the DRBsetting upon receipt of the end marker. When not receiving the endmarker, the UE may wait for the cancellation of the DRB setting untilreceiving the end marker, and cancel the DRB setting after receiving theend marker.

Although the example of canceling the DRB before the additional settingis disclosed, the DRB before the additional setting need not be canceledwhen the QoS to be mapped to the DRB before the additional settingexists. The MgNB should notify the UE of the reconfigured DRBconfiguration when the DRB before the additional setting isreconfigured.

For example, the New AS sublayer may insert an end marker as a protocolstack of inserting an end marker. One end marker may be inserted intoall the QoS flows to be mapped to the DRB to be additionally set. Thisfacilitates the control. Alternatively, the end marker may be insertedfor each QoS flow. The control for each QoS flow can be flexiblyperformed, and the malfunctions can be reduced.

In Step ST4914, the MgNB starts the MC setting of the DRB that has beenadditionally set for the QoS flow on which the MC is performed. In StepST4915, the MgNB, the SgNB 1 and the SgNB 2 that are to be used for theMC, and the UE mutually perform the MC setup processing. The methoddisclosed in the sixth embodiment should be applied to this MC setupprocessing. Since the radio bearer is set for the QoS flow on which theMC is performed, the method for setting the MC to the radio bearer canbe applied thereto.

Disclosed is a method, when the MC is set for each QoS flow, foradditionally setting the DRB for the QoS flow to which the MC is set.Here, a piece of data via the DRB before the additionally setting and apiece of data via the additionally set DRB are transferred to the New ASsublayer per QoS flow. Although the PDCP reorders the pieces of data inthe DRBs, it does not reorder the pieces of packet data later.

Thus, when orders of the piece of data of the DRB before theadditionally setting and the piece of data of the additionally set DRBfrom the PDCP are different, the New AS sublayer has a problem offailing to rearrange the pieces of data, that is, a problem of failingto ensure the in-sequence pieces of data.

A method for solving such a problem is disclosed. The New AS sublayerassigns a sequence number to data. The sequence number should be definedfor each QoS flow to be assigned to the data. Upon receipt of the piecesof the data from the PDCP, the New AS sublayer should perform reorderingusing the sequence numbers.

Another method is disclosed. The end marker is used. The pieces of datavia the additionally set DRB from the PDCP between additionally settingof the DRB and reception of the end marker are stored. A buffer forstoring the pieces of data should be provided. The pieces of dataranging from the DRB before the additional setting to an end markershould be processed to be transferred to the high-level NW or the upperlayer. Then, when the end marker appears, data via the additionally setDRB from the PDCP should be processed and transferred to the high-levelNW or the upper layer.

Consequently, correct orders of the pieces of packet data can beensured.

A buffer for storing data may be provided in the New AS sublayer, andthe New AS sublayer may perform these processes.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodshould be applied to the MgNB, and the SgNBs to which the MC is set foreach QoS flow.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method should be applied to theMgNB, and the SgNBs to which the MC is set for each QoS flow. The SR orthe BSR for each QoS flow may be provided and notified from the UE tothe base station side.

The MgNB can perform the MC on the UE for each QoS flow with such amethod. Since the MC can be performed for each QoS flow, the MC can becontrolled with QoS precision finer than that of the MC for each bearer.

The sixth embodiment discloses providing the MgNB with the routingfunctions for the SgNB s to which the MC is set. Such provision of therouting functions to the MgNB should be applied to the firstmodification of the sixth embodiment. A function of performing routingto a different SgNB for each QoS flow may be provided. In the presenceof a plurality of QoS flows on which the MC is performed, the MgNBperforms routing to a different SgNB for each of the QoS flows. The MgNBshould determine which SgNB routing is performed into, using a QoS flowidentifier.

The MgNB should define association between the QoS flows and the SgNBsinto which the routing is performed. The MgNB should notify the UE ofthe association. The MgNB should give the notification via the RRCsignaling. For example, the MgNB may include the association in the RRCconnection reconfiguration to notify the association. The MgNB maynotify the association when the MC is set to the UE. Consequently, theassociation between the QoS flows and the SgNBs to which data istransmitted can be set to the UE.

The UE may define the association between the QoS flows and the SgNBsinto which the routing is performed. The UE should notify the MgNB ofthe association. The UE should give the notification via the RRCsignaling. For example, the UE may include the association in the RRCconnection reconfiguration to notify the association. The UE canrequest, from the MgNB, which SgNB is used for each QoS flow.

When performing the routing to a different SgNB for each of the QoSflow, the MgNB may notify a QoS profile of the corresponding QoS flow inan additional request to the SgNB. Each SgNB may use the DRB settingcorresponding to the notified QoS profile. Each SgNB notifies the MgNBof the DRB setting corresponding to the QoS profile. The MgNB may notifythe UE of the DRB setting received from the SgNB as the DRB setting forthe MC. The MgNB should notify the UE via the RRC signaling. Forexample, the MgNB may notify the DRB setting corresponding to the QoSprofile with the RRC connection reconfiguration.

Consequently, the DRB configuration of the SgNB into which the routingis performed for each QoS flow can be set appropriate for the QoS of theQoS flow to be routed. Thus, the MC using the SgNBs with the DRBconfiguration appropriate for each QoS flow can be set.

The eNBs that are base stations in the LTE may be used as secondary basestations for the MC. The secondary base stations may include an eNB anda gNB. The method disclosed in the first modification of the sixthembodiment should be appropriately applied thereto. Since the secondarybase stations do not use the New AS sublayer in the first modification,the eNBs can be used as the secondary base stations.

The method disclosed in the first modification of the sixth embodimentcan configure the connection of one UE to one master base station and aplurality of secondary base stations even when the high-level NW is theNG-CN. This can increase the throughput of communication to be providedfor the UE. Moreover, the connection to a plurality of base stations canenhance the reliability.

The Seventh Embodiment

As previously described, Non-Patent Document 27 (R2-167583) proposes thesupport of the MC with the SCG bearer. The MC with the SCG bearerrequires an architecture and the setting method including the high-levelNW, such as a method of connection to the high-level NW. For example,when a plurality of SgNBs are used for the MC, problems arise includingwhat type of the bearer configuration should be used and how todistribute data to the plurality of SgNBs.

However, the disclosure of Non-Patent Document 27 and the conventionaltechnology do not clarify which architecture or setting method should beused. The seventh embodiment discloses an architecture and a settingmethod of the MC with the SCG bearer.

FIG. 28 illustrates an architecture of the MC. FIG. 28 illustrates thatthe high-level NW is an EPC, the master base station is a base stationin the LTE (eNB), and the secondary base stations are base stations inNR (gNBs). Although FIG. 28 illustrates the architecture on the basestation side, the architecture on the UE side is identical to that onthe base station side except for the high-level NW. One UE includes thePDCPs, the RLCs, the MACs, and the PHYs for the MeNB and the SeNBs thatare set for the MC.

FIG. 28 illustrates the use of the SCG split bearer. The high-level NWis connected to the SgNBs for the MC. The high-level NW routes thedownlink data into the SgNBs for the MC to transfer the data. Thehigh-level NW transfers the downlink data to the PDCPs without routingthrough the New AS sublayers of the SgNBs. Although data from thehigh-level NW may enter the New AS sublayers of the SgNBs, the data isnot processed by the New AS sublayers but passes through the New ASsublayers.

In each of the SgNBs, the data is processed by the PDCP, the RLC, theMAC, and the PHY, and then transmitted to the UE.

The data received by the UE from each of the SgNBs for the MC isprocessed by the PHY, the MAC, the RLC, and the PDCP for the SgNB, andthen transferred to the upper layer.

The UE routes the data from the upper layer into the SgNBs as the uplinkdata, and then transfers the data to the PDCPs for the SgNBs. The datais processed by the PDCP, the RLC, the MAC, and the PHY for each of theSgNBs, and then transmitted to the SgNB.

Disclosed is that the high-level NW routes data into the SgNBs for theMC. Thus, the high-level NW is provided with the routing functions forthe SgNBs. The S-GW of the U-plane functioning as the high-level NW maybe provided with the routing functions. The routing function may beadded as one function of the S-GW. The high-level NW is connected to aplurality of SgNBs to perform the MC without changing the E-RAB bearerthat is set between the high-level NW and the UE.

The routing functions should support both the downlink and the uplink.The routing functions may include a function of adding sequence numbersto pieces of packet data. The routing functions should performreordering using the sequence numbers.

FIG. 28 discloses providing the S-GW with the routing functions betweenthe S-GW and a plurality of SgNBs. As an alternative method, nodesdifferent from the S-GW may be provided with the routing functions. Thismakes the functional extension in the S-GW unnecessary.

The base station side may have the routing functions between the S-GWand the plurality of SgNBs. The routing function of any one of the SgNBsfor the MC may be used. Data is communicated between the S-GW and therouting function of the one of the SgNBs. With the routing function ofthe one of the SgNBs, data is routed into the other SgNBs.

This makes the functional extension in the S-GW unnecessary. Thefunctional extension of the base station side suffices. Thus, the systemis easily built.

A method for setting the MC with the SCG bearer is disclosed. Themethods disclosed in the sixth embodiment should be applied to theadditional request process from the MeNB to the SgNBs to be used for theMC and the MC setting from the MeNB to the UE.

A data forwarding method from the MeNB to the SgNBs is disclosed. Theproblem is which SgNB the data forwarding is performed to because aplurality of SgNBs are set in the MC. To solve this problem, the MeNBshould determine a SgNB as a data forwarding destination. The MeNBtransfers an SN status of the PDCP PDU to the determined SgNB to startthe data forwarding. The data forwarding is possible until path switchfrom the MeNB to the SgNB to be used for the MC is performed.

An SgNB as a data forwarding destination is set. When the MC isperformed using a plurality of SgNBs, the MeNB presets a predeterminedSgNB. The MeNB transfers the SN status and performs the data forwarding,to the set SgNB. The MeNB may notify, in the SgNB addition request forthe MC, the set SgNB that its own SgNB is an SgNB subject to dataforwarding. Since the SgNB can recognize the data forwarding from theMeNB, the malfunctions can be reduced.

The MeNB may notify the UE of information on the predetermined SgNB thatis set to a data forwarding destination. The MeNB may include theinformation in the settings of the MC to notify the information to theUE. The UE recognizes which SgNB the forwarded data is transmitted from.The UE may process the data from the SgNB earlier than the data on whichthe high-level NW has performed the routing function with the settingsof the MC, and transfer the data to the upper layer. This can correctthe orders of the pieces of packet data.

Another data forwarding method is disclosed. The MeNB may determine a

SgNB as a data forwarding destination for each packet data. Then, theMeNB similarly transfers the SN status of the PDCP PDU and performs thedata forwarding, to the determined SgNB. For example, assume that theMeNB has transmitted data up to the PDCP PDU whose SN is n−1. Whentransferring the next packet data to the SgNB 1, the MeNB transfers theSN status n and the next packet data to the SgNB 1. The SgNB 1 performsthe PDCP process on the packet data. Here, the PDCP assigns n as the SN.

When transferring the next packet to the SgNB 2, the MeNB transfers theSN status n+1 and the next packet data to the SgNB 2. The SgNB 2performs the PDCP process on the packet data. Here, the PDCP assigns n+1as the SN. Although the MeNB transfers n as the SN status aftercompletion of the transmission up to n−1, the MeNB may transfer n−1 asthe SN status. Upon receipt of the SN status, the SgNB should set n asthe SN of the PDCP PDU. Such transferring of the SN for each packet dataenables the MeNB to transfer data to a plurality of SgNBs for eachpacket data. The PDCP ensures the continuity of the SNs.

The MeNB may transfer a contiguous sequence of pieces of packet data tothe SgNB, not for each packet data. The MeNB transfers only the first SNof the contiguous sequence of pieces of packet data to the SgNB. TheMeNB counts the number of the pieces of packet data transferred to theSgNB, and calculates the SN of the next packet data to be transferred toanother SgNB, using the counted value. The MeNB transfers the calculatedSN status and the packet data to the other SgNB. This enables the MeNBto transfer the plural pieces of packet data to the SgNB continuously.The information to be communication between the base stations can bereduced more than that when the SN is transferred for each packet.

The UE may reorder pieces of packet data, using the SN of each PDCP. TheUE may reorder the pieces of packet data, using the SNs of the PDCPs ofthe MeNB and each

SgNB and transfer the pieces of packet data to the high-level NW.Alternatively, the UE may notify the high-level NW of information on theSNs from the PDCPs of the MeNB and each SgNB. Then, the high-level NWmay reorder the pieces of packet data using the SN information. Sincethe unified SNs are assigned to the MeNB and each SgNB, the orders ofthe pieces of packet data can be corrected.

A path switch method from the MeNB to the SgNB is disclosed. The MeNBnotifies the MME of the path switch information for the MC. Elevenexamples of the MC path switch information are hereinafter disclosed:

(1) bearer information for performing the path switch;

(2) identifiers of a plurality of SgNBs to which the MC is set;

(3) addresses of the plurality of SgNBs to which the MC is set;

(4) a path switch request;

(5) an identifier of a node with the routing function;

(6) an address of the node with the routing function;

(7) a request for activating the routing function;

(8) an identifier of the UE to which the MC is set;

(9) an identifier of its own MeNB;

(10) an address of its own MeNB; and

(11) combinations of (1) to (10) above.

In (1), information on the E-RAB bearer corresponding to the DRB towhich the

MC is set may be used as the bearer information for performing the pathswitch. The information on the E-RAB bearer may include an identifier ofthe E-RAB bearer. The MME can recognize the E-RAB bearer to which the MCis set.

In (2) and (3), the SgNBs to be path switch destinations may be used asthe plurality of SgNBs to which the MC is set. Upon receipt of the pathswitch request of (4), the S-GW or the node with the routing functionperforms the path switch to the SgNBs as the path switch destinations.

The MME notifies the S-GW of the MC path switch information receivedfrom the MeNB. The S-GW may notify the node with the routing function ofthe MC path switch information. When the S-GW is provided with the pathswitch function, the MC path switch information need not be notified tothe S-GW. Upon receipt of the MC path switch information, the S-GW orthe node with the routing function performs the path switch from theMeNB to a plurality of SgNBs to which the MC is set, and then starts therouting into the plurality of SgNBs.

When a predetermined SgNB is provided with the routing function, theMeNB may directly notify the predetermined SgNB of the MC path switchinformation. The MeNB should give the notification simultaneously withthe notification of the MC path switch information to the S-GW throughthe MME. The MC path switch information to be notified from the MeNB tothe S-GW through the MME may include the identifier or the address ofthe node with the routing function in (5) and (6) and the path switchrequest in (4). In response to the path switch request in (4), the S-GWperforms the path switch from the MeNB to the node with the routingfunction.

The path switch information to be directly notified from the MeNB to thepredetermined SgNB may include the identifiers or the addresses of theplurality of SgNBs to which the MC is set in (2) and (3), and therequest for activating the routing function in (7). The predeterminedSgNB routes the data received from the S-GW, into the plurality of SgNBsto which the MC is set and which include its own SgNB.

The MC path switch information to be notified from the MeNB to the MMEand from the MME to the S-GW may be included in the signaling formodifying the E-RAB to which the MC is set. Conventional messages shouldbe extendedly used, which does not require a new message. The controlcan be simplified.

As an alternative method, the path switch which the MeNB sets to the MMEand the MME sets to the S-GW may be set one by one to the SgNBs for theMC. The path switch destination via the conventional signaling formodifying the E-RAB is one SgNB, which may be used. The conventionalmessages should be used, which can simplify the control.

When the path switch is set one by one to the SgNBs for the MC, an SgNBshould be additionally set in response to a new path switch requestwhile the SgNBs that are path switch destinations set in response to aprevious path switch request are maintained. Information indicatingwhether the SgNBs previously set as the path switch destinations aremaintained may be provided as information for the path switch. The MeNBcan set the path switch to a plurality of the SgNBs by notifying theinformation to the S-GW through the MME.

FIGS. 29 and 30 illustrate an example sequence for setting the MC withthe SCG bearer. FIGS. 29 and 30 are connected across a location of aborder BL 2930. FIGS. 29 and 30 illustrate the use of the MeNB and twoSgNBs (SgNB 1 and SgNB 2). FIGS. 29 and 30 illustrate a method forsetting the SCGs of a plurality of SgNBs for the MC at one time. FIGS.29 and 30 illustrate that the S-GW is provided with the routingfunction.

Since the sequence illustrated in FIGS. 29 and 30 includes the samesteps as those of the sequence illustrated in FIGS. 19 and 20 , the samestep numbers are applied to the same Steps and the common descriptionthereof is omitted.

After transmitting the SgNB reconfiguration completion notifications forthe MC to the SgNB 1 and the SgNB 2 in Steps ST4207 and ST4219,respectively, the MeNB transfers the SN status for transferring data tothe SgNB 1 in Step ST5201, and starts transferring, to the SgNB 1, datafrom the S-GW through Steps ST5202 and ST5203.

Although the MeNB transfers data only to the SgNB 1 in FIGS. 29 and 30 ,it may transfer data to the SgNB 1 and the SgNB 2 for each data in thedisclosed method.

In Step ST5204, the MeNB notifies the MME of the signaling for modifyingthe E-RAB. The MeNB includes the MC path switch setting information inthe signaling for modifying the E-RAB to notify the information. In StepST5205, the MME notifies the S-GW of bearer modification signalingincluding the MC path switch setting information. Consequently, the S-GWcan recognize a plurality of SgNBs as path switch destinations.

The MME that has notifies the S-GW of the MC path switch settinginformation in Step ST5205 notifies the MeNB of the signaling indicatingcompletion of modification of the E-RAB. Consequently, the MeNBrecognizes that the path switch has been set to the SgNB 1 and the SgNB2 for the MC.

Upon receipt of the MC path switch setting information in Step ST5205,the S-GW transmits a packet indicating the end marker as the last packetdata to the MeNB to activate the path switch in Step ST5206. In StepST5207, the MeNB transfers the end marker to the SgNB 1. Consequently,the SgNB 1 recognizes termination of data from the MeNB.

In Step ST5209, the S-GW starts routing data into the SgNB 1 and theSgNB 2 to which the MC is set. This enables data communication among theUE, the SgNB 1, and the SgNB 2 and among the SgNB 1, the SgNB 2, and theS-GW. The UE and the plurality of SgNBs for the MC perform the MC withthe SCG bearer.

Disclosed is providing the plurality of SgNBs to be used for the MC withthe routing functions. Information for routing may be provided asinformation for the routing functions to determine which SgNB datashould be transmitted to. For example, the information may be a downlinkdata transmission state from each SgNB to the UE to be notified from itsown SgNB to the MeNB, which is disclosed in the sixth embodiment.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodshould be applied to the SgNBs for the MC.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method should be applied to theMeNB or the SgNBs for the MC.

The MeNB determines to perform the routing. Each SgNB notifies the MeNBof information for performing the routing. The MeNB calculates, forexample, the amount of data to be routed to each SgNB, using theinformation. The amount of data may be a data rate. The amount of datato be calculated may be an amount of data to be transmitted to each SgNBwith respect to the amount of total data. The MeNB notifies the MME ofthe amount of data to be routed to each SgNB. The MME notifies the S-GWof the amount of data to be routed to each SgNB. The S-GW notifies therouting function of the information. The routing function performs therouting using the amount of data.

This can adjust the amount of data to be routed to each SgNB. Moreover,each SgNB notifies the MeNB of the downlink data transmission state fromits own SgNB to the UE. Thus, the MeNB can use the downlink datatransmission state.

As an alternative method, the MME may determine to perform the routing.Each SgNB notifies the MeNB of information for performing the routing.Then, the MeNB notifies the MME of the information. Alternatively, eachSgNB may notify the MME of the information for performing the routing.Similarly as described above, the MME calculates, for example, theamount of data to be routed to each SgNB using the information, andnotifies the S-GW of the calculated amount of data. The S-GW notifiesthe routing function of the information. The routing function performsthe routing using the amount of data.

This can adjust the amount of data to be routed to each SgNB. The MME,which is a high-level device, determines to perform the routing. Thiscan facilitate the control when the MME and the S-GW are configured inthe same device.

As an alternative method, the S-GW may determine to perform the routing.Each SgNB notifies the MeNB of information for performing the routing.Then, the MeNB notifies the information to the MME, and the MME notifiesit to the S-GW. Alternatively, each SgNB may notify the MME of theinformation for performing the routing. Then, the MME may notify theS-GW of the information. Alternatively, each SgNB may notify the S-GW ofthe information for performing the routing.

Similarly as described above, the S-GW calculates, for example, theamount of data to be routed to each SgNB, using the information. TheS-GW notifies the routing function of the information. The routingfunction performs the routing using the amount of data.

This can adjust the amount of data to be routed to each SgNB. The S-GW,which is a high-level device in the U-plane, determines to perform therouting. This can control the routing of data in the U-plane.

As an alternative method, the node with the routing function maydetermine to perform the routing. Each SgNB notifies the MeNB of theinformation for performing the routing. Then, the information isnotified from the MeNB to the MME, from the MME to the S-GW, and fromthe S-GW to the node with the routing function. Alternatively, each

SgNB may notify the MME of the information for performing the routing.Then, the information may be notified from the MME to the S-GW and fromthe S-GW to the node with the routing function. Alternatively, each SgNBmay notify the S-GW of the information for performing the routing. Then,the S-GW may notify the node with the routing function of theinformation. Alternatively, each SgNB may notify the node with therouting function of the information for performing the routing.

Similarly as described above, the node with the routing functioncalculates, for example, the amount of data to be routed to each SgNB,using the information. The node with the routing function performs therouting using the amount of data.

This can adjust the amount of data to be routed to each SgNB. The nodewith the routing function determines to perform the routing. This canfacilitate the control over the routing of data, and reduce themalfunctions.

The routing function may be performed for each data. The routing isperformed to the SgNB s for each data. Alternatively, the same routingmay be performed for a predetermined duration. The data for thepredetermined duration is routed to the same SgNB. This enables flexiblerouting. The routing appropriate for a communication quality state ofeach SgNB is possible.

The eNBs that are base stations in the LTE may be used as secondary basestations for the MC. The secondary base stations may include an eNB anda gNB. The method disclosed in the seventh embodiment should beappropriately applied thereto. Since the secondary base stations do notuse the New AS sublayer in the seventh embodiment, the eNBs can be usedas the secondary base stations.

The method disclosed in the seventh embodiment can configure theconnection of one UE to a plurality of secondary base stations. This canincrease the throughput of communication to be provided for the UE.Moreover, the connection to a plurality of base stations can enhance thereliability. Since the MC with the SCG bearer can be set, thecommunication without routing through the MeNB can be provided. This canincrease the throughput of communication to be provided for the UE.

The First Modification of the Seventh Embodiment

The details of the MC with the SCG bearer in the presence of the New ASsublayer protocol have not yet been discussed. The first modification ofthe seventh embodiment discloses a method for performing the MC with theSCG bearer in the presence of the New AS sublayer protocol.

FIG. 31 illustrates an architecture of the MC with the SCG bearer. FIG.31 illustrates that the high-level NW is an NG-CN, the master basestation is a base station in NR (gNB), and the secondary base stationsare base stations in NR (gNBs). The master base station in NR isreferred to as the MgNB, and the secondary base stations in NR arereferred to as the SgNBs. The protocol configuration of the gNB includesthe New AS sublayer, the PDCP, the RLC, the MAC, and the PHY. The New ASsublayer is set higher than the PDCP.

Although the master base station is the gNB in NR in FIG. 31 , themaster base station may be an eNB obtained by adding the New AS sublayerto a base station in the LTE.

Although FIG. 31 illustrates the architecture on the base station side,the architecture on the UE side is identical to that on the base stationside except for the high-level NW. In one UE, the RLC, the MAC, and thePHY for the MgNB, the RLC, the MAC, and the PHY for each of the SgNBsset for the MC, the New AS sublayer, and the PDCP are configured.

FIG. 31 illustrates the use of the SCG bearer. The high-level NW isconnected to the SgNBs. The high-level NW routes the downlink data intothe SgNBs for the MC to transfer it. The New AS sublayer of the SgNBmaps the data to a DRB according to a QoS flow identifier. The PDCPprocesses the data for each of the mapped DRBs.

In each of the SgNBs, the data is processed by the PDCP, the RLC, theMAC, and the PHY for each of the DRBs, and then transmitted to the UE.

The data received by the UE from each of the SgNBs for the MC isprocessed by the PHY, the MAC, the RLC, the PDCP, and the New ASsublayer for the SgNB. The New AS sublayer separates the data into theQoS flows according to the QoS flow identifiers, and then transfers thepieces of data to the upper layer.

In the UE, the New AS sublayer for the SgNB maps, as the uplink data,the pieces of data from the upper layer to DRBs according to the QoSflow identifiers. Then, the

PDCP, the RLC, the MAC, and the PHY process the pieces of data for eachof the mapped DRBs, and then transmit the pieces of data to each of theSgNBs.

The data received by each of the SgNBs from the UE is processed by thePHY, the MAC, the RLC, and the PDCP, and then transferred to the New ASsublayer. The New AS sublayer separates the pieces of data into the QoSflows according to the QoS flow identifiers, and then transfers thepieces of data to the high-level NW.

A method for setting the MC with the SCG bearer is disclosed. The MC isset for each DRB. The MC is set with the SCG bearer for each DRB. Whenthe high-level NW sets the MC with the SCG bearer in the NG-CN, thefollowing problems mainly occur.

Conventionally, one PDU session tunnel (may be referred to as an N3tunnel) is set between the UPF and the gNB per PDU session, throughwhich communication is performed between the UPF and the gNB. However,when the SCG bearer is used, the high-level NW needs to communicate notonly with the MgNB but also with the SgNB. When the MC with the SCGbearer is performed, the high-level NW needs to communicate not onlywith the MgNB but also with a plurality of SgNBs. In such a case, how todeal with the PDU session tunnel is a problem.

Moreover, the following other problems occur. The routing has to beperformed to the plurality of SgNBs for the MC. Where the routingfunction is installed and which function is provided as the routingfunction are problems.

Moreover, following another problem occurs. The SgNB needs to set a DRBnecessary for the MC. What to do with a method for the SgNB to set theDRB necessary for the MC and a mapping method from the New AS sublayerof the SgNB is a problem.

The first modification of the seventh embodiment discloses a method forsolving such problems.

A plurality of PDU session tunnels can be set per PDU session betweenthe NG-CN and the RAN. The MgNB determines to set a plurality of PDUsession tunnels. For example, when the MgNB to be connected to the NG-CNperforms the MC with the SCG bearer, the MgNB determines to set theplurality of PDU session tunnels.

The MgNB notifies the high-level NW of a request for adding the PDUsession tunnels. The request should include PDU session tunnel additioninformation. The MgNB notifies the request to the UPF as a node of thehigh-level NW. The MgNB may notify the request to the AMF or the SMF asa node of the high-level NW. Then, the AMF or the SMF may notify therequest to the UPF. Nine examples of the PDU session tunnel additioninformation are disclosed below:

(1) a PDU session identifier;

(2) PDU session tunnel identifiers (may be the N3 tunnel identifiers);

(3) QoS flow identifiers to which the MC is set;

(4) an identifier of the SgNB to which the MC is set;

(5) an address of the SgNB to which the MC is set;

(6) an identifier of a node with the routing function;

(7) an address of the node with the routing function;

(8) information for requesting maintaining of the mapping method from aQoS profile to a QoS flow; and

(9) combinations of (1) to (8) above.

(1) may be any information for identifying the PDU session. Informationfor identifying the PDU session which the high-level NW has notified inestablishing the PDU session may be used. This can indicate which PDUsession the PDU session tunnel is to be added to.

(2) may be any information for identifying the PDU session tunnels thathave already been set. Information for identifying the PDU sessiontunnels which the high-level

NW has notified in establishing the PDU session may be used. This canspecify the PDU session tunnels that have already been set.

In (3), the number of the QoS flows on which the MC is performed may beone or more. (3) can indicate which QoS flow in the PDU session ismigrated to the PDU session tunnel.

(4) may be any information for identifying a SgNB to which thehigh-level NW sets the PDU session tunnel. For example, when the UPF isprovided with the routing function, the PDU session tunnel can be setfor a SgNB with the notified identifier.

(5) may be any information indicating the address of the SgNB to whichthe high-level NW sets the PDU session tunnel. For example, when the UPFis provided with the routing function, the PDU session tunnel can be setfor the SgNB with the notified address.

(6) may be any information for identifying the node with the routingfunction to which the high-level NW sets the PDU session tunnel. Forexample, when the node with the routing function is provided on the RANside, the PDU session tunnel can be set for the node with the routingfunction having the notified identifier.

(7) may be any information for identifying the address of the node withthe routing function to which the high-level NW sets the PDU sessiontunnel. For example, when the node with the routing function is providedon the RAN side, the PDU session tunnel can be set for the node with therouting function having the notified address.

(8) may be any information indicating that the mapping method from a QoSprofile to a QoS flow which migrates to the additionally set PDU sessiontunnel is identical to the method before the additional setting. Thehigh-level NW may map the QoS profile to the QoS flow using theinformation. The high-level NW may determine whether the mapping methodis set identical to that before the additional setting. The settingappropriate for a state of the high-level NW is possible.

The high-level NW may notify the MgNB that the mapping method isidentical to that before the additional setting if it is so. The MgNBcan map, for the SgNB to be used for the MC, a QoS flow identifier to aDRB in the New AS sublayer with the same setting as that before theadditional setting. This facilitates the setting of the SgNBs to whichthe MC is set.

When the mapping method is set different from that before the additionalsetting, the high-level NW notifies the MgNB of information on areconfigured mapping relationship between the QoS profile and the QoSflow. The high-level NW should notify the information by associating theQoS flow identifier with the QoS profile of the QoS flow. The MgNBnotifies the SgNB to be used for the MC of the information. The SgNBscan set, using the information, the mapping from the QoS flow identifierto the DRB in the New AS sublayer.

When the PDU session tunnel addition information does not include theinformation of (8), the high-level NW may determine whether the mappingmethod is set identical to that before the additional setting. When thePDU session tunnel addition information includes the information of (8),the high-level NW may set the mapping method identical to that beforethe additional setting according to the information of (8).

The timing at which the PDU session tunnel is additionally set isdisclosed. For example, upon receipt of the SgNB addition requestresponse from the SgNB to be used for the MC, the MgNB notifies thehigh-level NW of a request for adding the PDU session tunnel. Since theMgNB can give the notification upon finalization of the SgNB to be usedfor the MC, an unnecessary PDU session tunnel is not set.

For example, the MgNB notifies the high-level NW of a request for addinga PDU session tunnel together with a path switch request. The pathswitch request may include the PDU session tunnel addition information.Since the signaling for the path switch request can be used, the amountof signaling can be reduced.

The timing at which the PDU session tunnel is additionally set is notlimited to this. The PDU session tunnel should be additionally set afterthe MgNB determines to perform the MC using the SgNBs and before thehigh-level NW performs the path switch.

In response to the request for adding the PDU session tunnel from theMgNB, the high-level NW notifies the MgNB of a response to the requestfor adding the PDU session tunnel. The high-level NW should also notifyPDU session tunnel addition request response information. Twelveexamples of the PDU session tunnel addition request response informationare disclosed below:

(1) completion of the additional setting;

(2) rejection of the additional setting;

(3) a cause for rejection of the additional setting;

(4) a PDU session identifier;

(5) PDU session tunnel identifiers before the additional setting;

(6) a PDU session tunnel identifier additionally set;

(7) association information between the added PDU session tunnel and theSgNB;

(8) association information between the added PDU session tunnel and theQoS flow;

(9) a QoS profile of the QoS flow;

(10) an identifier of the UPF;

(11) an address of the UPF; and

(12) combinations of (1) to (11) above.

(6) may be any information for enabling the MgNB to identify theadditionally set PDU session tunnel.

The additionally set PDU session tunnel may be set as PDU sessionsub-tunnels associated with the PDU session tunnel before the additionalsetting. One or more PDU session sub-tunnels are set to a PDU sessiontunnel. This need not set a plurality of PDU session tunnels to one PDUsession. The conventional setting of one PDU session with one PDUsession tunnel can be maintained.

When the PDU session sub-tunnels are set, PDU session sub-tunnelidentifiers should be used as a replacement for the PDU session tunnelidentifier additionally set in the examples of the PDU session tunneladdition request response information. The PDU session tunnel identifierbefore the additional setting may be notified as well. The PDU sessiontunnel before the additional setting and the PDU session sub-tunnelidentifiers additionally set should be notified in association with oneanother.

A PDU session tunnel identifier may be used as a PDU session sub-tunnelidentifier. For example, a combination of a PDU session tunnelidentifier and a sub-number may be used as a PDU session sub-tunnelidentifier. For example, a PDU session sub-tunnel identifier=a PDUsession tunnel identifier+a sub-number may hold. The sub-number has onlyto be notified as information for identifying a PDU session sub-tunnel,which can reduce the amount of information.

When many SgNBs are used for the MC, the SgNBs should be provided withthe respective PDU session sub-tunnels. Thus, the number of the PDUsession tunnel identifiers need not be increased.

When the MgNB notifies the high-level NW of a request for adding a PDUsession tunnel together with a path switch request, the high-level NWmay include the PDU session tunnel addition request response informationin a response to the path switch request to notify the information. Thiscan reduce the amount of signaling.

With application of such a method, the PDU session tunnel isadditionally set between the high-level NW and the SgNB to be used forthe MC. Use of the additionally set PDU session tunnel enables thecommunication between the high-level NW and the SgNB. Thus, the MC withthe SCG bearer can be performed.

The routing functions are necessary for a plurality of SgNBs for the MC.The routing function disclosed in the seventh embodiment should beappropriately applied to a position at which the routing function isinstalled and the routing function. Although the high-level NW is theEPC in the seventh embodiment, the high-level NW should be the NG-CN inthe first modification of the seventh embodiment.

Since the high-level NW is the EPC, the seventh embodiment disclosesthat the high-level NW is connected to a plurality of SgNBs withoutchanging the E-RAB bearer setting. Since the high-level NW is the NG-CNin the first modification of the seventh embodiment, the high-level NWand the RAN use not the E-RAB bearer setting but the setting with theQoS flow.

The high-level NW side may be provided with the routing functions. Forexample, the UPF may be provided with the routing function.Alternatively, the routing function may be provided for a function ofthe UPF. When the UPF is provided with the routing function, a PDUsession tunnel should be additionally set between the UPF and the SgNBsfor the MC. The method for additionally setting the PDU session tunnelshould be applied thereto.

The routing function may be provided separately from the high-level NW.The routing function may be provided as a node on the RAN side. Therouting function may be provided in the node on the RAN side. Forexample, the routing function may be provided as one function of theSgNB. When the routing function is provided in the node on the RAN side,a PDU session tunnel should be additionally set between the UPF and thenode on the RAN side. Even when the MC is performed using a plurality ofSgNBs, one PDU session tunnel should be additionally set.

This enables data to be transferred between the UPF and the node on theRAN side which has the routing function. Mere addition of one PDUsession tunnel can simplify the configuration of a system including thehigh-level NW.

An interface between the base stations should be used for transferringdata between the node on the RAN side which has the routing function andthe SgNB to be used for the MC. The interface is, for example, Xn.

A routing function should be provided above the New AS sublayer, thatis, between the New AS sublayer and the high-level NW, as a method forproviding the node on the RAN side with the routing function. Data fromthe high-level NW is routed in a phase of packet data before the data isprocessed by the New AS sublayer. The pieces of packet data from the NewAS layers of the SgNBs for the MC are reordered based on the SNsassigned by the routing function, and transferred to the high-level NW.

Another method for providing the node on the RAN side with the routingfunction may be providing the routing function between the New ASsublayer and the PDCP. The data from the high-level NW is routed intothe PDCPs of the SgNBs for the MC in a phase after the data is processedby the New AS sublayer. The pieces of data from the PDCPs of the SgNBsfor the MC are reordered based on the SNs assigned by the routingfunction and transferred to the high-level NW.

The DRB may be set for each SgNB for the MC. For example, the DRB can beset according to a load state of the SgNB. As an alternative method, theSgNB that performs the routing function may be provided with one DRB.Each SgNB for the MC performs data communication within this DRB. TheDRB configuration of each SgNB should be set so that QoS profiles of allthe SgNBs for the MC are set to the DRB for the SCG bearer or to adesired QoS of the QoS flow.

When the routing function is provided in the node on the RAN side, whichgNB the routing function is provided to is a problem. This is becausethe gNB having the routing function is not necessarily used as the SgNBfor the MC. Thus, a gNB should be provided with the routing function inadvance. On and Off of the routing function should be installed.

A method for setting the SgNB that turns ON the routing function isdisclosed. The SgNB that turns ON the routing function may be referredto as an R-SgNB.

The high-level NW determines the R-SgNB. The AMF or the SMF functioningas a high-level NW may determine the R-SgNB. The AMF or the SMF maydetermine the R-SgNB, for example, when the PDU session tunnel isadditionally set. The AMF determine the R-SgNB to be connected to theUPF, using the SgNB identifier for the MC that is included in the PDUsession tunnel addition information to be notified from the MgNB to theAMF. The AMF notifies the MgNB of an identifier of the R-SgNB. The AMFmay include the identifier of the R-SgNB in the PDU session tunneladdition request response information to notify the identifier.

The MgNB notifies the R-SgNB of the PDU session tunnel addition requestresponse information. Upon receipt of the notification, the R-SgNB canbe connected to the UPF through the PDU session tunnel added to the PDUsession including the QoS flow on which the MC is performed. The MgNBshould notify the R-SgNB of a request for performing the routing betweenthe UPF and the SgNB for the MC. The request may include information onits own SgNB and information on the SgNB for the MC.

The information on its own SgNB includes an identifier and an address ofits own SgNB. The information on the SgNB for the MC includes anidentifier and an address of the SgNB for the MC. Upon receipt of therequest, the R-SgNB turns ON the routing function, and routes data ofthe QoS flow to be communicated through the PDU session tunnel, into theSgNB for the MC.

The MgNB may collectively notify the R-SgNB of the PDU session tunneladdition request response information and the request for performing therouting between the UPF and the SgNB for the MC. Alternatively, anotification of the PDU session tunnel addition request responseinformation, and a notification of the information on its own SgNB andthe information on the SgNB for the MC may be regarded as the requestfor performing the routing between the UPF and the SgNB for the MC.Since the notifications can be made via one signaling, the amount ofsignaling can be reduced.

The AMF includes at least one of the identifier and the address of theR-SgNB in the PDU session tunnel addition information to notify the UPFof the information. This enables the UPF to be connected to the R-SgNBthrough the PDU session tunnel added to the PDU session including theQoS flow on which the MC is performed. Thus, communication between theR-SgNB and the UPF is possible. The information may be included in thepath switch request to be notified from the AMF to the UPF to benotified.

Although the notification from the AMF to the UPF is disclosed, thenotification may be given from the AMF to the UPF through the SMF. Thenotification should be given, for example, in the absence of a directinterface between the AMF and the UPF.

The AMF may notify the MgNB to deactivate the R-SgNB. The AMF alsonotifies the UPF to deactivate the R-SgNB. The MgNB notifies the R-SgNBof a request for deactivating the routing between the UPF and the SgNBfor the MC. Upon receipt of the deactivating request, the R-SgNB turnsOFF the routing function to deactivate the routing.

The R-SgNB may be reconfigured. The AMF determines to change the R-SgNBto be connected to the UPF. The AMF notifies the MgNB to change theR-SgNB. The notification for setting the R-SgNB may be used for thisnotification. The R-SgNB after change should be notified as a settingtarget. Information on the R-SgNB before change may be notified as well.

The MgNB notifies the R-SgNB before change of the request fordeactivating the routing between the UPF and the SgNB for the MC. Uponreceipt of the deactivating request, the R-SgNB turns OFF the routingfunction to deactivate the routing. The MgNB notifies the R-SgNB afterchange of the request for performing the routing between the UPF and theSgNB for the MC. The notification of the request for performing therouting which is given to the R-SgNB may be used for this notification.Upon receipt of the request, the R-SgNB turns ON the routing function toperform the routing.

The AMF also notifies the UPF to change the R-SgNB. The notification ofadding the PDU session tunnel for the R-SgNB may be used for thisnotification. The R-SgNB after change should be notified as a settingtarget. Information on the R-SgNB before change may be notified as well.The UPF can change the connection from the R-SgNB before change to theR-SgNB after change, using the target PDU session tunnel. This enablesthe communication between the R-SgNB after change and the UPF.

The RAN side may have a function of deactivating the routing to a partof the SgNBs. The MgNB may notify the R-SgNB of the request fordeactivating the routing between the UPF and the SgNB for the MC,together with information on an SgNB to which the routing is deactivatedor information on an SgNB to which the routing is continued. Uponreceipt of the deactivating request, the R-SgNB deactivates the routingto the SgNB subject to the deactivation.

The MgNB may determine the R-SgNB. The MgNB should notify the high-levelNW of information on the determined R-SgNB. The MgNB should notify atleast one of an identifier and an address of the SgNB to which therouting function is set, as the information on the R-SgNB. The MgNB mayinclude the information in the PDU session tunnel addition requestinformation to notify the information.

The disclosed methods for the high-level NW to determine the R-SgNBshould be appropriately applied to the notification from the MgNB to thedetermined R-SgNB, and the notification of the information on the R-SgNBto be given from the AMF to the UPF.

The MgNB may also determine to deactivate the routing function of theR-SgNB and reconfigure the R-SgNB. The aforementioned methods should beappropriately applied thereto.

The MgNB may notify the UE to implement, deactivate, or reconfigure therouting function. The UE is provided with the routing function betweenthe upper layer and the New AS sublayer or between the upper layer andthe PDCP. The routing function should be identical to that on the NWside.

The MgNB should set and perform the data routing for each UE. Thisenables the NW side to recognize which SgNB is to be used.Alternatively, the UE may set and perform the data routing. Which SgNBdata is routed to can be determined according to the power consumptionor a load state of the UE.

A function of mapping the QoS flow to the SgNB for the MC may beprovided as the routing function. The high-level NW device may determinethe mapping. This is effective, for example, when the high-level NW,e.g., the UPF is provided with the routing function. The AMF functioningas a high-level NW may determine the mapping. The AMF notifies the UPFof the mapping. The UPF maps the QoS flow to the SgNB using the notifiedmapping.

The AMF may notify the MgNB of the mapping. The MgNB may notify the UEof the mapping. This enables the UE to map the QoS flow to the SgNB forthe MC also in the uplink communication.

A RAN node may determine the mapping. This is effective, for example,when the RAN-side node is provided with the routing function. The MgNBfunctioning as the RAN node may determine the mapping. The MgNB notifiesthe R-SgNB of the mapping. The SgNB maps the QoS flow to the SgNB, usingthe notified mapping.

The MgNB may notify the UE of the mapping. This enables the UE to mapthe QoS flow to the SgNB for the MC and vice versa also in the uplinkcommunication.

Consequently, the SgNB can be set for each QoS flow. The packet data ofa predetermined QoS flow can be communicated through a predeterminedSgNB. The throughput can be increased with the setting appropriate for aload state or the processing capability of the SgNB.

A method for the SgNB to establish the DRB necessary for the MC and amapping method from the New AS sublayer of the SgNB are disclosed.

The MgNB notifies each SgNB for the MC of information on the DRBsetting.

Nine examples of the information on the DRB setting are listed below:

(1) a DRB identifier subject to the MC;

(2) a DRB configuration subject to the MC;

(3) QoS flow identifiers mapped to the DRB subject to the MC;

(4) a QoS profile for each QoS flow;

(5) a PDU session identifier subject to the MC;

(6) a PDU session tunnel identifier additionally set;

(7) an identifier of a high-level device that establishes a PDU sessiontunnel;

(8) an address of the high-level device that establishes the PDU sessiontunnel; and

(9) combinations of (1) to (8) above.

Each SgNB sets the DRB for the MC, using the notified information on theDRB setting. Each SgNB sets the mapping to the DRB set from the New ASsublayer, according to the notified information. The settings of the DRBs in the SgNB s may be different from one another. The DRB identifiersmay also be different. The MgNB may notify each SgNB for the MC of theinformation on the DRB setting, via the SgNB reconfiguration completesignaling.

The MgNB may notify each SgNB for the MC of a request for establishingthe PDU session tunnel. The information on the DRB setting may beappropriately applied to information on the request for establishing thePDU session tunnel. The information on the

DRB setting and the information for establishing the PDU session tunnelmay be notified together. The notifications may be given via onesignaling. This can reduce the amount of signaling.

Each SgNB notifies the MgNB of DRB setting response information. Eightexamples of the DRB setting response information are listed below:

(1) an identifier of its own SgNB;

(2) an address of its own SgNB;

(3) acceptance of the DRB setting;

(4) rejection of the DRB setting;

(5) a cause for rejection of the DRB setting;

(6) a DRB configuration set by its own SgNB;

(7) a DRB identifier set by its own SgNB; and

(8) combinations of (1) to (7) above.

The MgNB sets the MC to the UE. The MgNB may notify a result of the DRBsetting from each SgNB for the MC as settings of the MC. The firstmodification of the sixth embodiment should be appropriately applied tomethods for setting the MC and notifying the setting from the MgNB tothe UE. Although the MCG split bearer is disclosed as a type of bearerin the first modification of the sixth embodiment, the SCG bearer may beapplied in the first modification of the seventh embodiment.

Such methods enable the high-level NW to set the MC with the SCG bearerin the NG-CN. The settings of the MC can be made for each DRB. The MCcan be performed between the UE and the MgNB and between the UE and eachSgNB for the MC. This can increase the throughput of the DRB to whichthe MC is set.

FIG. 32 is a conceptual diagram illustrating a dataflow when the MC withthe SCG bearer is set for each DRB. Assume that the mapping relationshipbetween the QoS flows and the DRBs before the MC is set is the oneillustrated in FIG. 21 . Assume a DRB on which the MC is performed asthe DRB 1. The QoS flow 1 and the QoS flow 2 are mapped to the DRB 1.

As illustrated in FIG. 32 , the MgNB additionally sets a PDU sessiontunnel on the SgNB side for the MC to set the DRB 1 to the MC with theSCG bearer. FIG. 32 illustrates that the node with the routing functionis provided separately from the high-level NW. Thus, the PDU sessiontunnel is additionally set between the high-level NW and the node withthe routing function. When the routing function is provided in thehigh-level NW, the PDU session tunnel is additionally set between thehigh-level NW and the SgNBs for the MC.

The QoS flow 1 and the QoS flow 2 which are mapped to the DRB to whichthe MC is set are communicated through the added PDU session tunnel. Thepacket data which the high-level NW maps to the QoS flow 1 and the QoSflow 2 is communicated through the added PDU session tunnel.

The node with the routing function routes data into the SgNBs for theMC. Each of the SgNBs sets the DRB for the MC, using information on theDRB 1 to which the MC is set, where the information is notified from theMgNB. FIG. 32 illustrates the use of the same setting in each SgNB asthat of the DRB 1 set by the MgNB. FIG. 32 illustrates the case of theDRB identifier identical to that set by the MgNB.

The data mapped to the QoS flow 1 and the QoS flow 2 is transferred tothe New AS sublayer of each of the SgNBs, and mapped to the DRB 1 in theNew AS sublayer. This enables each of the SgNBs for the MC to processthe QoS flow mapped to the DRB 1 to which the MC is set.

The MgNB should notify a configuration of each of the SgNBs on which theMC is performed and the DRB configuration set to the SgNB. For example,the method for notifying the DRB configuration from the MgNB to the UE,which is disclosed in the sixth embodiment, should be applied to thisnotification. The UE can set the DRB configuration set to each of theSgNBs. The same applies to the uplink data. This can implement the MCfor each DRB.

FIGS. 33 to 35 illustrate an example sequence for setting the MC withthe SCG bearer when the high-level NW is the NG-CN. FIGS. 33 to 35 areconnected across locations of borders BL3334 and BL3435. FIGS. 33 to 35illustrate the use of the MgNB and two SgNBs (SgNB 1 and SgNB 2). Sincethe sequence illustrated in FIGS. 33 to 35 includes the same steps asthose of the sequences illustrated in FIGS. 19 and 20 and FIGS. 29 and30 , the same step numbers are applied to the same Steps and the commondescription thereof is omitted.

In Steps ST5501 and ST5502, the MgNB notifies the SgNB 1 and the SgNB 2,respectively, of the SgNB addition requests. The signaling for additionrequest should include the information on the DRB setting. Examples ofthe information on the DRB setting include an identifier and aconfiguration of a DRB subject to the MC, an identifier of the QoS flowmapped to the DRB subject to the MC, a QoS profile for each QoS flow,and a PDU session identifier subject to the MC.

The MgNB may determine a QoS profile setting for each of the SgNBs towhich the MC is set to satisfy the QoS profile of the QoS flow on whichthe MC is performed.

The MgNB may notify each of the SgNBs to which the MC is set of the DRBconfiguration to be requested from the SgNB. The MgNB may set the DRBconfiguration identical to the DRB configuration before the setting.Alternatively, the MgNB may determine a bearer configuration so that thebearer configuration of the SgNB to which the MC is set satisfies theQoS profile of the QoS flow on which the MC is performed.

Upon receipt of the information on the DRB settings from the MgNB, theSgNB 1 and the SgNB 2 set the DRBs for mapping the QoS flows subject tothe MC. In Steps ST5503 and ST5504, the SgNB 1 and the SgNB 2,respectively, notify the MgNB of addition request responses to theaddition requests. The signaling for addition request response shouldinclude the DRB setting response information. The addition requestresponse is, for example, the DRB setting acceptance. Examples of theDRB setting response information include the DRB identifier and itsconfiguration that are set by its own SgNB, and the identifier and theaddress of its own SgNB. The SgNB 1 and the SgNB 2 may notify the ASsettings set by its own SgNBs.

Upon receipt of the signaling for SgNB addition request response fromeach of the SgNBs to be used for the MC, the MgNB notifies thehigh-level NW of a request for adding the PDU session tunnel to set theMC with the SCG bearer in Step ST5505. The MgNB should include the PDUsession tunnel addition information in the signaling for the request foradding the PDU session tunnel to notify the information. Examples of thePDU session tunnel addition information include a PDU session identifiersubject to the MC, a PDU session tunnel identifier subject to the MC, aQoS flow identifier subject to the MC, and an identifier and an addressof the SgNB for the MC.

In Step ST5506, the AMF/SMF notifies the UPF of a PDU session tunneladdition request. Similarly as described above, the AMF/SMF shouldinclude the PDU session tunnel addition information in the signaling forthe request for adding the PDU session tunnel to notify the information.

Upon receipt of the notification of the PDU session tunnel additionrequest and the PDU session tunnel addition information in Step ST5506,the UPF additionally sets the PDU session tunnel for the SgNBs to beused for the MC.

In Step ST4302, the MgNB notifies the UE of the settings of the MC. TheMgNB notifies, as the settings of the MC, the SCG configuration of eachof the SgNBs for the MC and the DRB configuration set by the SgNB. TheRRCConnectionReconfiguration for setting the RRC connection may be usedas the signaling. The MgNB may notify the SCG bearer as a type ofbearer.

Upon receipt of the SCG configurations and the DRB configurations of theSgNB 1 and the SgNB 2 in Step ST4302, the UE sets the MC to the MgNB,the SgNB 1, and the SgNB 2 according to the settings. In Step ST4303,the UE gives the MgNB the RRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification including completionof the settings of the MC.

Upon recognizing that the UE has completed the settings of the MC, theMgNB notifies the signaling indicating the completion of the additionalsetting of the SCG of each of the SgNBs to the SgNB 1 in Step ST4207 andto the SgNB 2 in Step ST4219. The SgNB 1 and the SgNB 2 recognizecompletion of the connection setting with the UE for the MC.

The MgNB may notify the SgNB 1 and the SgNB 2 of requests forestablishing the PDU session tunnels, using the signalings forcompletion of the additional setting of the SCG in Step ST4207 andST4219, respectively. The information on the DRB setting should beincluded in the signaling for completion of the additional setting ofthe SCG as the information on the request for establishing the PDUsession tunnel.

Examples of the information on the DRB setting include the identifier ofthe DRB subject to the MC, the identifier of the QoS flow mapped to theDRB subject to the MC, the PDU session identifier subject to the MC, thePDU session tunnel identifier additionally set, and the identifier andthe address of the high-level device that establishes the PDU sessiontunnel.

Consequently, the PDU session tunnel is additionally set between theAMF/SMF and the SgNBs to be used for the MC. This enables datacommunication between the SgNBs for the MC with the SCG bearer and thehigh-level NW.

In Steps ST4208 and ST4220, the UE performs the RA procedures with theSgNB 1 and the SgNB 2, respectively, to establish synchronizationtherewith. In Steps ST5201 to ST5203, the MgNB transfers the SN statusand data to the SgNB 1. The method disclosed in the seventh embodimentshould be appropriately applied to the transferring of data.

In Step ST5508, the MgNB notifies the AMF/SMF of a PDU session tunnelswitching request. The MgNB requests the AMF/SMF to change the QoS flowincluded in the DRB subject to the MC from the PDU session tunnel beforesetting the MC to the PDU session tunnel additionally set for the SgNBsto be used for the MC. The signaling for the PDU session tunnelswitching request should include information for switching the PDUsession tunnel.

Eight examples of the information for switching the PDU session tunnelwill be described below:

(1) QoS flow identifiers mapped to the DRB subject to the MC;

(2) a PDU session identifier subject to the MC;

(3) a PDU session tunnel identifier additionally set;

(4) an identifier of a high-level device that establishes a PDU sessiontunnel;

(5) an address of the high-level device that establishes the PDU sessiontunnel;

(6) an identifier of the SgNB to be used for the MC;

(7) an address of the SgNB to be used for the MC; and

(8) combinations of (1) to (7) above.

Similarly as in Step ST5508, the AMF/SMF notifies the UPF of the PDUsession tunnel switching request in Step ST5509. Upon receipt of the PDUsession tunnel switching request, the UPF transmits a packet indicatingthe end marker as the last packet data to the MgNB in Step ST5206, andswitches to the PDU tunnel additionally set for the SgNB to be used forthe MC, using information notified in the PDU session tunnel switchingrequest. In Step ST5207, the MgNB transfers the end marker to the SgNB1. Consequently, the SgNB 1 recognizes termination of data from theMgNB.

The AMF/SMF, which has notified the UPF of the PDU session tunnelswitching request in Step ST5509, notifies the MgNB of a PDU sessiontunnel switching request response. Consequently, the MgNB recognizes theswitching to the PDU session tunnel additionally set for the SgNB 1 andthe SgNB 2 for the MC.

Upon receipt of the MC path switch setting information in Step ST5509,the UPF transmits the packet indicating the end marker as the lastpacket data to the MgNB to activate the path switch in Step ST5206. InStep ST5207, the MgNB transfers the end marker to the SgNB 1.Consequently, the SgNB 1 recognizes termination of data from the MgNB.

In Step ST5210, the packet data is routed to each SgNB for the MC withthe routing function provided in the UPF. In Steps ST5211 to ST5214,data is communicated between the SgNB 1, the SgNB 2, and the UPF.

This enables the MC with the SCG bearer when the high-level NW is theNG-CN. The MgNB can set the MC with the SCG bearer to the UE. The UE canperform the MC through connecting with a plurality of SgNBs for the MC.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodshould be applied to the SgNB for the MC.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method should be applied to theMgNB and the SgNB for the MC.

A method for restoring the settings of the MC with the SCG bearer to theMCG bearer is disclosed. When the PDU session tunnel for the PDU sessionsubject to the MC is set between the MgNB and the high-level NW, theMgNB should cancel the PDU session tunnel set with the SgNBs, and usethe PDU session tunnel between the MgNB and the high-level NW for theQoS flow included in the DRB subject to the MC.

When the PDU session tunnel for the PDU session subject to the MC is notset between the MgNB and the high-level NW, the MgNB should set the PDUsession tunnel between the MgNB and the high-level NW. The MgNB shouldcancel the PDU session tunnel set with the SgNBs, and use the PDUsession tunnel set between the MgNB and the high-level NW for the QoSflow included in the DRB subject to the MC.

The MgNB should cancel the settings for the MC which are set between theSgNBs and the UE. The aforementioned methods should be appropriatelyapplied to these methods.

Another method for setting the MC with the SCG bearer is disclosed. TheMC is set for each QoS flow. The New AS sublayer performs the MC withthe SCG bearer on one or more of the QoS flows that are mapped to theDRB.

When the high-level NW sets the MC with the SCG bearer for each QoS flowin the NG-CN, the following problems as well as the aforementionedproblems occur.

When the MgNB maps a plurality of QoS flows to one DRB and sets the MCfor each of the plurality of QoS flows, the QoS flows to be mapped stillremain in the DRB even after the MC is set. In such a case, the PDCPprocesses data and assigns the SN to the data even after the MC is set.

When the connection with the UE migrates from the MgNB to the SgNBthrough the MC with the SCG bearer, data that is being processed by theMgNB needs to be transferred to the SgNB. In such a case, it isconventionally sufficient that the SN status is transferred and the PDCPof the SgNB sets the SN using the transferred SN. This enables the UE toreorder the PDCPs using the SNs.

However, when a plurality of QoS flows are mapped to a DRB to which theMC is set, not only pieces of data of QoS flows to which the MC is setbut also pieces of data of QoS flows to which the MC is not set may betransferred to the SgNB. Since the PDCP of the SgNB processes the piecesof data of the QoS flows to which the MC is not set, a problem offailing to normally reorder the pieces of data of the QoS flows to whichthe MC is set occurs. The same applies to the uplink.

As a method for solving such a problem, a transferring process for eachQoS flow is performed. Data to be transferred from the MgNB to the SgNBshould be limited to the QoS flows to which the MC is set. The MgNBmakes a determination using a QoS flow identifier added to data. TheMgNB transfers, to the SgNB, the data of the QoS flow to which the MC isset, whereas the MgNB does not transfer the data of the QoS flow towhich the MC is not set.

The SgNB processes the data of the QoS flow that has been transferred tothe SgNB. The MgNB processes the data of the QoS flow that is nottransferred to the SgNB. With such a transferring process for each QoSflow, the data in the SgNB can be normally processed.

An alternative method for solving such a problem is additionally settinga DRB for a QoS flow on which the MC is performed and mapping the QoSflow on which the MC is performed to the additionally set DRB. Throughsetting the MC to the additionally set DRB, the MC can be set to the QoSflow mapped to the DRB.

Consequently, the QoS flow mapped to the additionally set DRB does notremain after the MC is set. Thus, the pieces of data of the QoS flows onwhich the MC is performed and which is mapped to the additionally setDRB are transferred to the SgNB. Since the PDCP of the SgNB processesthe pieces of data of the QoS flows on which the MC is performed, thepieces of data can be normally reordered. The same applies to theuplink.

The method for additionally setting the DRB for the QoS flow on whichthe MC is performed, which is disclosed in the first modification of thesixth embodiment, should be appropriately applied to a method foradditionally setting the DRB for the QoS flow on which the MC isperformed and mapping the QoS flow on which the MC is performed to theadditionally set DRB.

FIG. 36 is a conceptual diagram illustrating a dataflow when the MC withthe SCG bearer is set for each QoS flow. Assume that the mappingrelationship between the QoS flows and the DRBs before the MC is set isthe one illustrated in FIG. 21 . Assume a DRB on which the MC isperformed as the DRB 1. The QoS flow 1 and the QoS flow 2 are mapped tothe DRB 1.

As illustrated in FIG. 36 , the MgNB additionally sets a PDU sessiontunnel on the SgNB side for the MC to set the QoS flow 1 in the DRB 1 tothe MC with the SCG bearer. FIG. 36 illustrates that the node with therouting function is provided separately from the high-level NW. Thus,the PDU session tunnel is additionally set between the high-level NW andthe node with the routing function. When the routing function isprovided in the high-level NW, the PDU session tunnel is additionallyset between the high-level NW and the SgNBs for the MC.

The QoS flow 1 to which the MC is set is communicated through the addedPDU session tunnel. The packet data which the high-level NW maps to theQoS flow 1 is communicated using the added PDU session tunnel.

The node with the routing function routes the data into the SgNBs forthe MC. Each of the SgNBs sets a DRB for the MC, using information onthe DRB 1 to which the MC is set, where the information is notified fromthe MgNB. Each of the SgNBs may set the DRB for the MC, usinginformation on the QoS profile of the QoS flow 1 to which the MC is set,where the information is notified from the MgNB.

FIG. 36 illustrates the use of the setting different from that of theDRB 1 set by the MgNB to the SgNBs. FIG. 36 illustrates the use of a DRBidentifier (DRBY 1) different from that set by the MgNB.

The data mapped to the QoS flow 1 is transferred to the New AS sublayerof each of the SgNBs, and mapped to the DRBY 1 in the New AS sublayer.This enables each of the SgNBs for the MC to process the QoS flow 1 towhich the MC is set.

On the other hand, the MC is not set to the QoS flow 2 in the DRB 1, andthe QoS flow 2 is communicated on the MgNB side. The MgNB maintains, inthe DRB 1, the DRB on the MgNB side for the QoS flow 2. The MgNB mayreconfigure the DRB 1. For example, the MgNB should reconfigure the DRBconfiguration appropriate for the QoS flow 2 after the MC is set.

FIG. 36 illustrates the use of the same setting as that of the DRB 1 setby the MgNB. FIG. 36 illustrates the use of the DRB identifier (DRBY 1)identical to that set by the MgNB.

The QoS flow 2 is communicated through the PDU session tunnelestablished between the high-level NW and the MgNB before the MC is set.The data which the high-level NW maps to the QoS flow 2 is transferredto the New AS sublayer of the MgNB, and mapped to the DRB 1 in the NewAS sublayer. This enables the MgNB to process the QoS flow 2 to whichthe MC is not set.

The MgNB should notify the UE of the reconfigured DRB configuration. TheMgNB should notify the configuration of each of the SgNBs to which theMC is set, and the DRB configuration set to the SgNB. For example, themethod for notifying the DRB configuration from the MgNB to the UE,which is disclosed in the sixth embodiment, should be applied to thisnotification. The UE can reconfigure the DRB configuration set on theMgNB side, and set the DRB configuration to each of the SgNB s. The sameapplies to the uplink data. This can implement the MC for each QoS flow.

FIGS. 26 and 27 should be applied to a sequence for setting the MC withthe SCG bearer for each QoS flow. Steps ST4902 to ST4913 should beperformed for additionally setting the DRB for the QoS flow on which theMC is performed. The DRB for the QoS flow on which the MC is performedis additionally set, and the QoS flow on which the MC is performed ismapped to the additionally set DRB. Through setting the MC to theadditionally set DRB, the MC can be set to the QoS flow mapped to theDRB.

Consequently, the QoS flow mapped to the additionally set DRB does notremain after the MC is set. Thus, the pieces of data of the QoS flows onwhich the MC is performed and which is mapped to the additionally setDRB are transferred to the SgNB. Since the PDCP of the SgNB processesthe pieces of data of the QoS flows on which the MC is performed, thepieces of data can be normally reordered. The same applies to theuplink.

In Step ST4914, the MgNB starts the settings of the MC with the SCGbearer of the DRB that has been additionally set for the QoS flow onwhich the MC is performed. In Step ST4915, the MgNB, the SgNB 1 and theSgNB 2 that are to be used for the MC, the AMF/SMF, the UPF, and the UEmutually perform the MC setup processing with the SCG bearer. FIGS. 33to 35 should be applied to this MC setup processing.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodshould be applied to the SgNBs to which the MC is set for each QoS flow.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method should be applied to theMgNB, and the SgNBs to which the MC is set for each QoS flow. The SR orthe BSR for each QoS flow may be provided and notified from the UE tothe base station side.

This enables the MC with the SCG bearer when the high-level NW is theNG-CN. The MgNB can set the MC with the SCG bearer to the UE. The UE canperform the MC through connecting with a plurality of SgNBs for the MC.

The MgNB can perform the MC with the SCG bearer on the UE for each QoSflow. Since the MC can be performed for each QoS flow, the MC can becontrolled with QoS precision finer than that of the MC for each bearer.

The eNBs that are base stations in the LTE may be used as base stationsfor the MC that are not connected to the high-level NW. The basestations may include an eNB and a gNB. The method disclosed in the firstmodification of the seventh embodiment should be appropriately appliedthereto. Since the base stations for the MC that are not connected tothe high-level NW do not use the New AS sublayer in the firstmodification, the eNBs can be used as the base stations.

The method disclosed in the first modification of the seventh embodimentcan configure the connection of one UE to a plurality of secondary basestations even when the high-level NW is the NG-CN. This can increase thethroughput of communication to be provided for the UE. Moreover, theconnection to a plurality of base stations can enhance the reliability.Since the MC with the SCG bearer can be set, the communication withoutrouting through the MgNB can be provided. This can increase thethroughput of communication to be provided for the UE.

The Eighth Embodiment

The seventh embodiment discloses the MC with the SCG bearer. When therouting function is provided for the high-level NW in the MC using theSCG bearer, communication is performed between the high-level NW andeach SgNB to be used for the MC. Enabling such communication requiresnotification of the setting of each SgNB to the high-level NW, whichcomplicates the settings of the MC. This causes a problem of increasingthe amount of signaling between the high-level NW and a base station.

Moreover, information necessary for the routing needs to be transmittedto the node with the routing function. This also causes the problem ofincreasing the amount of signaling between the high-level NW and thebase station.

The eighth embodiment discloses a method for solving such a problem. AnSCG split bearer for splitting data into the other SgNBs is provided.

With the conventional SCG split bearer, the SgNB is connected to thehigh-level NW device, and the SgNB splits data from the high-level NWinto its own SgNB and the MeNB. The same applies to the uplinkcommunication. In other words, the DC using the MeNB and one SgNB isperformed.

With the SCG split bearer disclosed in the eighth embodiment, the SgNBis connected to the high-level NW device, and the SgNB splits data fromthe high-level NW into its own SgNB and the other SgNBs. Since the MeNBis used for communication in the C-Plane, etc., in this sense, the MCusing the MeNB, the SgNB to be connected to the high-level NW, and theother SgNBs is performed. The same applies to the uplink communication.The number of the other SgNBs may be one or more. The SgNB to beconnected to the high-level NW device may be referred to as a P-SgNB.

FIG. 37 illustrates an architecture of the MC. FIG. 37 illustrates thatthe high-level NW is an EPC, the master base station is a base stationin the LTE (eNB), and the secondary base stations are base stations inNR (gNBs). Although FIG. 37 illustrates the architecture on the basestation side, the architecture on the UE side is identical to that onthe base station side except for the high-level NW. One UE includes theRLC, the MAC, and the PHY for the MeNB, the RLC, the MAC, and the PHYfor each of SgNBs set for the MC, and the PDCP.

FIG. 37 illustrates the use of the SCG split bearer. The high-level NWis connected to one SgNB (P-SgNB). The other SgNBs for the MC areconnected to the P-SgNB. The high-level NW transfers the downlink datato the P-SgNB. The high-level NW transfers the downlink data to the PDCPwithout routing through the New AS sublayers of the P-SgNB. Althoughdata from the high-level NW may enter the New AS sublayer of the P-SgNB,the data is not processed by the New AS sublayers but passes through theNew AS sublayers.

The PDCP of the P-SgNB processes the downlink data. Even when the numberof the other SgNBs is more than one, the PDCP assigns one serialsequence number (SN) to each data. The data to which the SN is assignedis split into its own P-SgNB and the other SgNBs. The pieces of splitdata are transmitted to the RLCs of its own P-SgNB and the other SgNBsto be processed by the RLCs, the MACs, and the PHYs of the P-SgNB andthe other SgNBs, and then transmitted to the UE.

The pieces of data received by the UE from the P-SgNB and the otherSgNBs are processed by the PHYs, the MACs, and the RLCs for the P-SgNBand the other SgNBs, and then transferred to the PDCP. The PDCP performsreordering based on the SNs assigned to the pieces of data transferredfrom layers for the P-SgNB and the other SgNBs, and transfers the piecesof data to the upper layer.

The PDCP in the UE processes the pieces of data from the upper layer asthe uplink data. Similarly in the downlink, even when the number of theother SgNBs is more than one, the PDCP assigns one serial sequencenumber (SN) to each data in the uplink. The data to which the SN isadded is split into the RLCs for the P-SgNB and the other SgNBs to betransferred. The transferred data is processed by the RLCs, the MACs,and the PHYs for the P-SgNB and the other SgNBs, and then transmitted tothe P-SgNB and the other SgNBs.

The pieces of data received by the P-SgNB and the other SgNBs from theUE are processed by the PHYs, the MACs, and the RLCs for the P-SgNB andthe other SgNBs, and then transferred to the PDCP of the P-SgNB. ThePDCP of the P-SgNB reorders the pieces of data based on the SNs assignedthereto, and then transfers the pieces of data to the high-level NW.

The routing function for the split bearer may be provided in gNB. Therouting function for the SgNB to be used for the MC is provided in thegNB. The routing function provided in the P-SgNB may be used for the MCwith the SCG split bearer. The method disclosed in the sixth embodimentshould be appropriately applied to the routing function.

A method for setting the MC with the SCG bearer is disclosed. The MeNBdetermines all the SgNBs to be used for the MC. The MeNB determines theP-SgNB and the other SgNBs to be used for the MC. The MeNB sets thebearer configuration of each of the SgNBs to be used for the MC, andthen requests the SgNB to set the bearer configuration. The MeNBnotifies each of the SgNBs of a request for setting the bearerconfiguration of the SgNB. The MeNB may notify a type of bearer as abearer configuration. The MeNB may notify the SCG split bearer as a typeof bearer. The MeNB may notify the SCG split bearer using the P-SgNB andthe other SgNBs.

A method for additionally setting the SgNB is disclosed as the settingsof the MC with the SCG split bearer. First, the MeNB sets the SCG bearerto the SgNB to be connected to the high-level NW (P-SgNB). Next, theMeNB sets the SCG split bearer to the P-SgNB and the other SgNBs to beused for the MC. The method for setting the DC with the SCG bearershould be applied to the initial setting of the SCG bearer to theP-SgNB.

A method for setting the SCG split bearer to the P-SgNB and the otherSgNBs to be used for the MC is disclosed. The MeNB requests the otherSgNBs to add an SgNB for the SCG split bearer. The MeNB includesinformation on adding the SgNB for the SCG split bearer in the request,and notifies the other SgNBs of the information. Seven examples of theinformation to be notified from the MeNB to the other SgNBs aredescribed below:

(1) information indicating the setting of the SCG split bearer;

(2) an SCG split bearer configuration;

(3) information on the P-SgNB;

(4) information on the DRB to which the MC is set;

(5) a bearer configuration to be set to each SgNB, such as a QoSprofile;

(6) information on the UE to which the MC is set; and

(7) combinations of (1) to (6) above.

The SCG split bearer configuration of (2) includes informationindicating that the notified SgNB is one of the other SgNBs, andinformation indicating the split from the P-SgNB. The information on theP-SgNB of (3) includes the identifier and the address of the P-SgNB. Theinformation may include information instructing connection with theP-SgNB. Alternatively, the request may indicate an instruction forconnecting to the P-SgNB. The information on the DRB to which the MC isset in (4) may be an identifier of the DRB. The information may includethe DRB configuration.

Upon receipt of these pieces of information, the SgNB recognizes thatits own SgNB is one of the other SgNBs to be used for the MC with theSCG split bearer. The SgNB sets the SCG configuration and the DRBconfiguration of its own SgNB, based on, for example, the QoS profile ofthe bearer to which the MC is set. Also, the SgNB makes a setting ofcommunication using the P-SgNB and the SCG split bearer.

The MeNB requests the P-SgNB to change to the SCG split bearer. The MeNBnotifies the P-SgNB of the additional setting of the SgNB for the SCGsplit bearer. The request for changing to the SCG split bearer mayinclude setting information of the SgNB to be added for the SCG splitbearer. The MeNB includes information on adding the SgNB for the SCGsplit bearer in the request, and notifies the P-SgNB of the information.Nine examples of the information to be notified from the MeNB to theP-SgNB are described below:

(1) information indicating the setting of the SCG split bearer;

(2) information indicating the P-SgNB;

(3) the SCG split bearer configuration;

(4) information on a SgNB included in the SCG split bearer;

(5) information on the DRB to which the MC is set;

(6) a bearer configuration to be set to each SgNB, such as a QoSprofile;

(7) information on the high-level NW;

(8) information on the UE to which the MC is set; and

(9) combinations of (1) to (8) above.

The information indicating the P-SgNB of (2) may be, for example, aflag. This can reduce the amount of information. The information may be,for example, a 1-bit flag. For example, 1 indicates the P-SgNB, and 0indicates a non-P-SgNB. The information indicating the P-SgNB may be,for example, an identifier of the P-SgNB.

For example, parameters of the P-SgNB and the other SgNBs are defined.An identifier of a gNB to be the P-SgNB is included in the parameter ofthe P-SgNB, and identifiers of gNBs to be the other SgNBs are includedin the parameters of the other SgNBs. Since this can integrate pieces ofinformation to be notified to the P-SgNB and the other SgNBs, thecomplexity in setting the SCG split bearer can be avoided.

The information on the high-level NW of (7) may be an identifier and anaddress of the S-GW. Alternatively, the information may include anidentifier and an address of the MME. This enables connection betweenthe P-SgNB and the high-level NW.

Upon receipt of these pieces of information, the SgNB recognizes thatits own SgNB is the P-SgNB to be used for the MC with the SCG splitbearer. The SgNB changes the SCG bearer to the SCG split bearer usingthe other SgNBs. The SgNB sets the SCG configuration and the DRBconfiguration of its own SgNB, based on, for example, the QoS profile ofthe bearer to which the MC is set. The SgNB may maintain the SCGconfiguration and the DRB configuration that are used for the SCGbearer. The SgNB makes settings of communication with other SgNBs usingthe SCG split bearer.

The P-SgNB and other SgNBs each of which has set the SCG configurationand the DRB configuration of its own SgNB for the SCG split bearernotify the MeNB of responses to the requests. The responses may indicateacknowledgement or negative acknowledgement. When the response indicatesacknowledgement, each SgNB should notify the MeNB of the SCGconfiguration and the DRB configuration of its own SgNB. When theresponse indicates negative acknowledgement, each SgNB should include acause for the rejection in the response to notify the cause.

Although disclosed is that the MeNB may notify the P-SgNB of theinformation on an SgNB included in the SCG split bearer in requestingchange to the SCG split bearer, the SgNB should be an SgNB that hasreceived the acknowledgement. Consequently, the MC with the SCG splitbearer can be set between the MeNB and each SgNB.

It is simultaneously possible to set the SCG bearer to the P-SgNB andchange the setting of the P-SgNB to the SCG split bearer. It is alsopossible to initially set the SCG split bearer to the other SgNBs, andthen set the SCG bearer to the P-SgNB and change the setting of theP-SgNB from the SCG bearer to the SCG split bearer. Such a setting maybe applied, for example, when the MeNB recognizes that the SgNB is usedas the P-SgNB or another SgNB. Thus, the setting can be simplified.

According to the disclosed method, the MeNB requests the other SgNBs toadditionally set an SgNB for the SCG split bearer. The MeNB mayadditionally set the SgNB for the SCG split bearer to the other SgNBsthrough the P-SgNB. The MeNB notifies the P-SgNB of the request foradditionally setting the SgNB for the SCG split bearer to the otherSgNBs. Upon receipt of the request, the P-SgNB notifies the other SgNBsof the requests for additionally setting the SgNB for the SCG splitbearer.

The other SgNBs may notify the MeNB of responses to the requests throughthe P-SgNB. The other SgNBs notifies the P-SgNB of the responses to therequests. The P-SgNB notifies the MeNB of the responses to the requestsfrom the other SgNBs. The P-SgNB may recognize the details of theresponses to the requests of the other SgNBs.

Consequently, the MeNB has only to communicate with the P-SgNB. Thus,the settings of the MC with the SCG split bearer can be simplified. TheMeNB may notify, via the same signaling, the P-SgNB of change to the SCGsplit bearer and the other SgNBs of the request for additionally settingthe SCG split bearer. This can reduce the amount of signaling.

Another method for additionally setting the SgNB is disclosed. The MeNBrequests each SgNB to be used for the MC to set the SCG split bearerwithout requesting the P-SgNB to set the SCG bearer. The MeNB mayrequest each SgNB to be used for the MC to change the setting from theMCG bearer to the SCG split bearer using the SgNB.

The MeNB should include the information on adding the SgNB for the SCGsplit bearer in the request to notify the information, as an example ofthe information to be included in the request. The MeNB includes, in therequest, the information on adding the SgNB for the SCG split bearer,which is notified from the MeNB to the P-SgNB, to notify the P-SgNB ofthe information. The MeNB includes, in the request, the information onadding the SgNB for the SCG split bearer to be notified from the MeNB tothe other SgNBs to notify the other SgNBs of the information.

Upon receipt of these pieces of information, the SgNB recognizes thatits own SgNB is the P-SgNB or one of the other SgNBs to be used for theMC with the SCG split bearer. The SgNB changes the MCG bearer to the SCGsplit bearer with the SgNB. The SgNB sets the SCG configuration and theDRB configuration of its own SgNB, based on, for example, the QoSprofile of the bearer to which the MC is set. The SgNB makes settings ofcommunication using the SCG split bearer with the P-SgNB or the otherSgNBs.

The P-SgNB and the other SgNBs each of which has set the SCGconfiguration and the DRB configuration of its own SgNB for the SCGsplit bearer notify the MeNB of responses to the requests. The responsesmay indicate acknowledgement or negative acknowledgement. When theresponse indicates acknowledgement, each SgNB should notify the MeNB ofthe SCG configuration and the DRB configuration of its own SgNB. Whenthe response indicates rejection, each SgNB should include a cause forthe rejection in the response to notify the cause.

The MeNB may additionally set an SgNB for the SCG split bearer to theother SgNBs through the P-SgNB. The aforementioned methods should beappropriately applied thereto. The same applies to the response to theadditional setting request.

This enables the settings of the MC with the SCG split bearer withoutsetting to the SCG bearer. Thus, changing the setting to the SCG splitbearer can be simplified.

The MeNB may temporarily restore the SCG bearer set to the SgNB to theMCG bearer and change the MCG bearer to the SCG split bearer. The MeNBrestores the setting of the SgNB to which the SCG bearer is set, fromthe SCG bearer to the MCG bearer. Next, the MeNB changes the setting ofeach SgNB to which the MC is set with the SCG split bearer, from the MCGbearer to the SCG split bearer. The aforementioned method should beapplied thereto.

The MeNB notifies the UE to which the MC is set of the settings of allthe SgNBs to be used for the MC with the SCG split bearer. The MeNB mayinclude, in the settings, information indicating the SCG split bearer asa type of bearer to notify the information. The MeNB may include, in thesettings, information indicating that the SCG split bearer is the SCGsplit bearer using the SgNB to notify the information. The MeNB mayinclude information indicating which one among all the SgNBs is theP-SgNB in the settings to notify the information.

The method disclosed in the sixth embodiment should be appropriatelyapplied to this setting method. With the information, the UE makessettings of communication with all the SgNBs to be used for the MC withthe SCG split bearer. This enables the UE to communicate with all theSgNBs to be used for the MC with the SCG split bearer.

The P-SgNB may determine the other SgNBs for the SCG split bearer. Sincethe MeNB need not to make the determination, there is no need for eachSgNB to notify the MeNB of information for the determination. This canreduce the amount of signaling.

The MeNB may notify the P-SgNB of an instruction for changing to the SCGsplit bearer. In response to the notification, the P-SgNB determines theother SgNBs for the SCG split bearer. The MeNB may simultaneously notifythe P-SgNB of the additional setting of the SCG bearer and theinstruction for changing to the SCG split bearer. The P-SgNB sets theSCG bearer and changes the SCG bearer to the SCG split bearer.

This enables the MeNB to determine the timing to activate changing tothe SCG split bearer. The P-SgNB determines the SgNB to which the MC isset.

The MeNB may notify the P-SgNB that change to the SCG split bearer ispermitted. In response to the notification, the P-SgNB can determine theother SgNBs for the SCG split bearer by its own decision. This enablesthe P-SgNB to determine the timing to activate changing to the SCG splitbearer after the permission notification from the MeNB. The P-SgNBdetermines the SgNB to which the MC is set.

The P-SgNB may determine to change to the SCG split bearer. The P-SgNBcan change to the SCG split bearer without any notification on itschange from the MeNB. This enables the SgNB to which the SCG bearer isset to always determine the timing to activate changing to the SCG splitbearer. The SgNB to which the SCG bearer is set functions as the P-SgNB,and determines the SgNB to which the MC is set.

When the P-SgNB changes to the SCG split bearer, the P-SgNB may notifythe MeNB of information indicating the change. The MeNB can recognizewhether the MC with the SCG split bearer is performed between the P-SgNBand the other SgNBs.

A method for the P-SgNB to set the SCG split bearer is disclosed. TheP-SgNB requests the other SgNBs to be used for the MC one by one toadditionally set the SgNB for the SCG split bearer. Alternatively, theP-SgNB may request, at one time, the other SgNBs to be used for the MCto additionally set the SgNB. The method disclosed in the sixthembodiment should be appropriately applied to both of the methods.

The MeNB notifies the P-SgNB of information on determining the SCG splitbearer. Nine examples of the information are described below:

(1) information indicating the P-SgNB;

(2) information instructing the setting of the SCG split bearer;

(3) information indicating that the SCG split bearer may be set;

(4) information indicating that the P-SgNB may determine and perform theSCG split bearer;

(5) information on the DRB on which the MC is performed;

(6) a bearer configuration to be set to the P-SgNB, such as a QoSprofile;

(7) information on the high-level NW;

(8) information on the UE to which the MC is set; and

(9) combinations of (1) to (8) above.

Upon receipt of the information, the P-SgNB can recognize that its ownP-SgNB may determine the other SgNBs for the SCG split bearer. If theMeNB sets the SCG bearer in advance and the SCG bearer need not bechanged to the bearer configuration at that time, the MeNB need notnotify the bearer configuration to be set to the P-SgNB, such as a QoSprofile in (6). Alternatively, the information may indicate the samesetting. The P-SgNB can recognize the bearer configuration and the QoSprofile that should be set with the SCG split bearer.

The P-SgNB notifies the other SgNBs for the SCG split bearer of arequest for setting the SCG split bearer. Seven examples of informationto be included in the request are described below:

(1) information indicating the setting of the SCG split bearer;

(2) the SCG split bearer configuration;

(3) information on the P-SgNB;

(4) information on the DRB to which the MC is set;

(5) a bearer configuration to be set to each SgNB, such as a QoSprofile;

(6) information on the UE to which the MC is set; and

(7) combinations of (1) to (6) above.

Upon receipt of the information, the other SgNBs can recognize thesetting of the SCG split bearer with the P-SgNB. The other SgNBs can setthe SCG configuration and the DRB configuration of its own SgNB, usingthe bearer configuration to be set to the P-SgNB, such as a QoS profilein (5).

Each of the other SgNBs to which the P-SgNB additionally sets the SgNBfor the SCG split bearer sets the SCG configuration and the DRBconfiguration of its own SgNB. The other SgNBs notifies the P-SgNB ofresponses to the request. The method for notifying the request responseshould be applied to this notification. Consequently, the P-SgNB canrecognize the settings of the other SgNBs.

The P-SgNB notifies the UE to which the MC is set of the settings of allthe SgNBs to be used for the MC with the SCG split bearer. The P-SgNBmay include, in the settings, information indicating the SCG splitbearer as a type of bearer to notify the information. The P-SgNB mayinclude, in the settings, information indicating that the SCG splitbearer is the SCG split bearer using the SgNB to notify the information.The P-SgNB may include which one among all the SgNBs is the P-SgNB inthe settings to notify the information.

The method disclosed in the sixth embodiment should be appropriatelyapplied to this setting method. With the information, the UE makessettings of communication with all the SgNBs to be used for the MC withthe SCG split bearer. This enables the UE to communicate with all theSgNBs to be used for the MC with the SCG split bearer.

Such a method saves the MeNB from recognizing the SgNB to be used forthe MC with the SCG split bearer. This makes the signaling between theMeNB and the other SgNBs unnecessary. Thus, the amount of signaling canbe reduced.

The P-SgNB may notify the MeNB of the SCG configuration and the DRBconfiguration of its own P-SgNB, and the SCG configurations and the DRBconfigurations of the other SgNBs. The P-SgNB may notify these pieces ofinformation as information associated with information on each of theSgNBs. The P-SgNB may notify these pieces of information as a responseto an instruction for changing to the SCG split bearer from the

MeNB or as a response to a notification from the MeNB which indicatesthat change to the SCG split bearer is possible.

Alternatively, the P-SgNB may notify these pieces of information via thesignaling separately provided. These pieces of information may beincluded in a notification of a response to the setting of the SCGbearer. The P-SgNB may include, in these pieces of information,information indicating that the SCG bearer has been changed to the SCGsplit bearer to notify the information. Consequently, the MeNB canrecognize the setting of each of the SgNBs.

When the MeNB can recognize the setting of each of the SgNBs, the MeNBmay notify the UE to which the MC is set of the settings of all theSgNBs to be used for the MC with the SCG split bearer. Theaforementioned pieces of information should be applied to information tobe included in the notification. The method disclosed in the sixthembodiment should be appropriately applied to this setting method. Withthe information notified from the MeNB, the UE makes settings ofcommunication with all the SgNBs to be used for the MC with the SCGsplit bearer. This enables the UE to communicate with all the SgNBs tobe used for the MC with the SCG split bearer.

Consequently, the MeNB can notify the UE of the settings of all theSgNBs to be used for the MC with the SCG split bearer, similarly to theconventional DC. The MeNB can change the bearer type to be used for theMC, which can avoid complexity in the control over the MC.

The data forwarding should be performed for preventing the loss in datawhen the SCG split bearer is set. The method on the MC with the SCGbearer, which is disclosed in the seventh embodiment, should beappropriately applied to the data forwarding method. The MeNB shouldtransfer the SN status and data to the P-SgNB.

When the MeNB initially sets the SCG bearer to the P-SgNB, the dataforwarding should be performed with the setting. Since the P-SgNB isused for both the SCG bearer and the SCG split bearer, the dataforwarding is unnecessary when the SCG bearer is changed to the SCGsplit bearer.

When the SCG split bearer is set, the MeNB notifies the high-level NW ofa path switch request from the MeNB to the P-SgNB. The method disclosedin the seventh embodiment should be appropriately applied thereto. Thepath switch should be performed only to the P-SgNB. As disclosed in theseventh embodiment, the signaling for modifying the E-RAB may be used.

When the MeNB initially sets the SCG bearer to the P-SgNB, the pathswitch should be performed with the setting. Since the P-SgNB is usedfor both the SCG bearer and the SCG split bearer, the path switch isunnecessary when the SCG bearer is changed to the SCG split bearer.

The method disclosed in the sixth embodiment should be appropriatelyapplied to information for routing data from the P-SgNB to the otherSgNBs. The other SgNBs should notify the P-SgNB of the information. TheP-SgNB performs the routing using the information to achieve the DRBconfigurations and the QoS profiles set to its own P-SgNB and the otherSgNBs. When the P-SgNB cannot achieve them, the P-SgNB may request theMeNB to change the SCG split bearer.

This can set the MC with the SCG split bearer to the UE. The UE canperform the MC with the SCG split bearer between the P-SgNB and theother SgNBs.

FIGS. 38 to 40 illustrate an example sequence for setting the MC withthe SCG split bearer. FIGS. 38 to 40 are connected across locations ofborders BL3839 and BL3940. FIGS. 38 to 40 illustrate the use of the MeNBand two SgNBs (SgNB 1 and SgNB 2). FIGS. 38 to 40 illustrate a methodfor initially setting the SCG bearer and then changing the setting tothe SCG split bearer. Since the sequence illustrated in FIGS. 38 to 40includes the same steps as those of the sequences illustrated in FIGS.17 and 18 and FIGS. 29 and 30 , the same step numbers are applied to thesame Steps and the common description thereof is omitted.

In Step ST4202, the MeNB determines to set the DC with the SCG bearer tothe UE. In Steps ST4203 to ST4208, Steps ST5201 to ST5203, and StepsST6201 to ST6207, the UE, the MeNB, the SgNB 1, the S-GW, and the MMEset the DC with the SCG bearer.

In Step ST6208, the SgNB 1 determines to perform the MC using the SCGsplit bearer with the SgNB 2. The SgNB 1 functions as the P-SgNB. InStep ST6209, the SgNB 1 notifies the SgNB 2 of a request foradditionally setting the SgNB for the SCG split bearer. The SgNB 1includes, in the notification, information to be included in the requestfor setting the SCG split bearer which is notified from the P-SgNB tothe other SgNBs for the SCG split bearer, to notify the information.

Upon receipt of the notification of the information in Step ST6209, theSgNB 2 sets the SCG configuration and the DRB configuration to its ownSgNB and notifies the SgNB 1 functioning as the P-SgNB of a response tothe request for additionally setting the SgNB for the SCG split bearerin Step ST6210. Here, the SgNB 2 notifies the acknowledgement. Theresponse should include information on the SCG configuration and the DRBconfiguration that are set by its own SgNB.

In Step ST6211, the P-SgNB notifies the UE of the settings of the MCwith the SCG split bearer. The settings of the MC should includeinformation on the SCG configuration and the DRB configuration that areset by its own P-SgNB, and the SCG configurations and the DRBconfigurations that are set by the other SgNBs. The P-SgNB may give thisnotification via the signaling for the RRC connection reconfiguration.

The UE makes settings of communication with the SgNB 1 and the SgNB 2using the settings of the MC with the SCG split bearer. In Step ST6212,the UE notifies the SgNB 1 of completion of the settings. The UE maygive this notification via the signaling for the RRC connectionreconfiguration complete notification. In Step ST6213, the SgNB 1notifies the SgNB 2 of completion of the settings of the MC with the SCGsplit bearer.

In Step ST6214, the UE performs the RA procedure with the SgNB 2 tosynchronize with the SgNB 2. This enables the UE to communicate with theSgNB 2. In Step ST6215, the SgNB 1 splits data between its own SgNB 1and the SgNB 2. Although FIG. 40 illustrates the routing function, thesplit function may replace the routing function because the data issplit into two SgNBs of the SgNB 1 and the SgNB 2.

Consequently, in Steps ST6216 to ST6219, the UE, the SgNB 1, the SgNB 2,and the S-GW perform data communication using the MC with the SCG splitbearer. The UE, the MeNB, the SgNB 1, the SgNB 2, and the S-GW performdata communication using the MC with the SCG split bearer because the UEand the MeNB perform communication for setting the MC which isindependent of the DRB.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodmay be applied to the P-SgNB and the other SgNBs. When the MeNB isconfigured as a replacement for one of the other SgNBs, the method maybe applied to the P-SgNB, the MeNB, and the other SgNBs.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method may be applied to the P-SgNBand the other SgNBs. When the MeNB is configured as a replacement forone of the other SgNBs, the method may be applied to the P-SgNB, theMeNB, and the other SgNBs.

The base stations to be split off from the P-SgNB for the MC may includethe MeNB. The MeNB may be set as a replacement for one of the otherSgNBs for the MC. The aforementioned method should be applied thereto.The use of the MeNB can reduce the number of the base stations to whichthe UE is connected.

The method disclosed in the eighth embodiment can set the MC with theSCG split bearer to the UE.

The method disclosed in the eighth embodiment can configure theconnection of one UE to a plurality of secondary base stations. This canincrease the throughput of communication to be provided for the UE.Moreover, the connection to a plurality of base stations can enhance thereliability. Since the MC with the SCG split bearer can be set, thehigh-level NW need not be connected to the plurality of secondary basestations. Thus, the complexity in the control between the high-level NWand the base stations can be avoided.

The First Modification of the Eighth Embodiment

The first modification of the seventh embodiment discloses the MC withthe SCG bearer in the presence of the New AS sublayer protocol. In theMC with the SCG bearer, when the routing function for the SgNBs to beused for the MC is provided in the high-level NW, the PDU session tunnelneeds to be established between the high-level NW and the SgNBs. Thiscomplicates the setting. The amount of information necessary fornotifying the setting of the PDU session tunnel increases.

The first modification of the eighth embodiment discloses a method forsolving such a problem. An SCG split bearer for splitting data into theother SgNBs is provided. The eighth embodiment should be appropriatelyapplied to this method. The eighth embodiment differs from the firstmodification in that the high-level NW is the EPC in the eighthembodiment, whereas the high-level NW is the NG-CN in the firstmodification. This difference is mainly disclosed.

The PDU session tunnel is established between the P-SgNB and thehigh-level NW. The P-SgNB may be an SgNB that establishes the PDUsession tunnel with the high-level NW. The number of the other SgNBs maybe one or more. Similarly as in the eighth embodiment, the SgNB to beconnected to the high-level NW may be referred to as the P-SgNB.

FIG. 41 illustrates an architecture of the MC. FIG. 41 illustrates thatthe high-level NW is an NG-CN, the master base station is a base stationin NR (gNB), and the secondary base stations are base stations in NR(gNBs). Although the master base station is the gNB in NR in FIG. 41 ,the master base station may be an eNB obtained by adding the New ASsublayer to a base station in the LTE.

Although FIG. 41 illustrates the architecture on the base station side,the architecture on the UE side is identical to that on the base stationside except for the high-level NW. One UE includes the New AS sublayer,the PDCP, the RLC, the MAC, and the PHY for the MgNB, the New ASsublayer, the PDCP, the RLC, the MAC, and the PHY for the P-SgNB set forthe MC, and the RLCs, the MACs, and the PHYs for the other SgNBs.

FIG. 41 illustrates the use of the SCG split bearer. The high-level NWis connected to one SgNB (P-SgNB). The other SgNBs for the MC areconnected to the P-SgNB. The high-level NW transfers the downlink datato the P-SgNB. The New AS sublayer of the P-SgNB maps the data to DRBsaccording to QoS flow identifiers. The data is transferred to the PDCPfor each of the mapped DRBs, and then processed by the PDCP.

The PDCP of the P-SgNB processes the downlink data. Even when the numberof the other SgNBs is more than one, the PDCP assigns one serialsequence number (SN) to each data. The data to which the SN is assignedis split into its own P-SgNB and the other SgNBs. The pieces of splitdata are transmitted to the RLCs of its own P-SgNB and the other SgNBs,and processed by the RLCs, the MACs, and the PHYs of the P-SgNB and theother SgNBs, and then transmitted to the UE.

The pieces of data received by the UE from the P-SgNB and the otherSgNBs are processed by the PHYs, the MACs, and the RLCs for the P-SgNBand the other SgNBs, and then transferred to the PDCP. The PDCP performsreordering based on the SNs assigned to the pieces of data transferredfrom layers for the P-SgNB and the other SgNBs, and transfers the piecesof data to the New AS sublayer. The New AS sublayer separates the piecesof data into the QoS flows according to the QoS flow identifiers, andthen transfers the pieces of data to the upper layer.

The UE processes the pieces of data from the upper layer as the uplinkdata in the New AS sublayers. The New AS sublayers map the pieces ofdata to DRBs according to QoS flow identifiers, and then transfer thepieces of data to the PDCPs for each of the mapped DRB s. Similarly inthe downlink, even when the number of the other SgNBs is more than one,the PDCPs assign one serial sequence number (SN) to each data in theuplink.

The data to which the SN is assigned is split into the RLCs for theP-SgNB and the other SgNBs to be transferred. The transferred data isprocessed by the RLCs, the MACs, and the PHYs for the P-SgNB and theother SgNBs, and then transmitted to the P-SgNB and the other SgNBs.

The pieces of data received by the P-SgNB and the other SgNBs from theUE are processed by the PHYs, the MACs, and the RLCs for the P-SgNB andthe other SgNBs, and then transferred to the PDCP of the P-SgNB. ThePDCP of the P-SgNB reorders the pieces of data based on the SNs assignedthereto, and then transfers the pieces of data to the New AS sublayer.The New AS sublayer separates the pieces of data into the QoS flowsaccording to the QoS flow identifiers, and then transfers the pieces ofdata to the high-level NW.

A method for setting the MC with the SCG split bearer is disclosed. TheMC is set for each DRB. The MC with the SCG split bearer is set for eachDRB. Since the P-SgNB needs the New AS sublayer, the method for settingthe MC with the SCG bearer which is disclosed in the first modificationof the seventh embodiment should be appropriately applied to the settingof the P-SgNB. The method for setting the MC with the MCG split bearer,which is disclosed in the first modification of the sixth embodiment,should be appropriately applied to the settings of the other SgNBs.

The first modification of the seventh embodiment describes theoccurrence of mainly three problems when the MC with the SCG bearer isset, and discloses the method for solving such problems. The SCG splitbearer also causes problems of how to deal with the PDU session tunnel,and what to do with the method for the SgNB to set the DRB necessary forthe MC and the mapping method.

The method disclosed in the first modification of the seventh embodimentshould be appropriately applied to how to deal with the PDU sessiontunnel with the SCG split bearer. The PDU session tunnel should beadditionally set between the P-SgNB and the high-level NW. Since theother SgNBs are connected through the P-SgNB, the PDU session tunnelneed not be additionally set to the other SgNB s.

The method disclosed in the first modification of the seventh embodimentshould be appropriately applied also to the problem on the mappingmethod from the New AS sublayer of the P-SgNB. The setting of the DRBnecessary for the MC and the mapping from the New AS sublayer should beperformed on the P-SgNB using the new AS sublayer. These processes areunnecessary for the other SgNBs.

The first modification of the sixth embodiment discloses, in thesettings of the MC using the MCG split bearer, the splitting and routingmethods for a plurality of SgNB s. The SCG split bearer also requiresthe splitting and routing methods which the P-SgNB applies to the otherSgNBs. The method disclosed in the first modification of the sixthembodiment should be appropriately applied to these methods. Thisenables the splitting and routing from the P-SgNB to the other SgNBs.

For example, the method for splitting and routing all the QoS flows inthe DRB, the method for splitting and routing a predetermined QoS flowin the DRB, and the method for performing routing to a predeterminedSgNB for each of the QoS flows should be appropriately applied thereto.The methods produce the same advantages. The method disclosed in theeighth embodiment should be appropriately applied to information for therouting. The P-SgNB can determine to perform the routing for the otherSgNBs.

Such methods enable the settings of the MC with the SCG split bearerwhen the high-level NW is the NG-CN. The settings of the MC can be madefor each DRB. The MC can be performed among the UE, the P-SgNB, and theother SgNBs. This can increase the throughput of the DRB to which the MCis set.

FIG. 42 is a conceptual diagram illustrating a dataflow when the MC withthe SCG split bearer is set for each DRB. Assume that the mappingrelationship between the QoS flows and the DRBs before the MC is set isthe one illustrated in FIG. 21 . Assume a DRB on which the MC isperformed as the DRB 1. The QoS flow 1 and the QoS flow 2 are mapped tothe DRB 1.

As illustrated in FIG. 42 , the MgNB additionally sets a PDU sessiontunnel to the SgNB 1 to be connected to the high-level NW in order toset the MC with the SCG split bearer to the DRB 1. The PDU sessiontunnel should be additionally set between the high-level NW and the SgNB1 (P-SgNB). The PDU session tunnel need not be additionally set betweenthe other SgNBs (SgNB 2, SgNB 3) and the high-level NW.

The QoS flow 1 and the QoS flow 2 which are mapped to the DRB to whichthe MC is set are communicated through the added PDU session tunnel. Thepacket data which the high-level NW maps to the QoS flow 1 and the QoSflow 2 is communicated through the added PDU session tunnel.

FIG. 42 illustrates the use of the same setting as that of the DRB 1 setby the MgNB to the P-SgNB. FIG. 42 illustrates the use of the DRBidentifier identical to that set by the MgNB.

The data mapped to the QoS flow 1 and the QoS flow 2 is transferred tothe New AS sublayer of the P-SgNB, and mapped to the DRB 1 in the New ASsublayer. This enables the P-SgNB to process the QoS flows mapped to theDRB 1 to which the MC is set.

The PDCP of the P-SgNB splits and routes the data of the QoS flow 1 andthe QoS flow 2 that are mapped to the DRB 1 into its own P-SgNB and theother SgNBs. Similarly in the downlink, the PDCP splits and routes thedata of the QoS flow 1 and the QoS flow 2 mapped to the DRB 1 in the NewAS sublayer of the UE as the uplink data to the RLCs for the P-SgNB andthe other SgNBs.

Not the DRB 1 set in the downlink but a default DRB may be used in theuplink. In such a case, the PDCP should split and route the data of theQoS flow 1 and the QoS flow 2 for which the UE uses the default DRB tothe RLCs for the P-SgNB and the other SgNBs. In the P-SgNB, the PDCPreorders the pieces of data from the P-SgNB and the other SgNBs usingthe SNs. The New AS layer separates the pieces of data according to theQoS flow identifiers for each of the QoS flows, and then transfers thepieces of separated data to the high-level NW.

Setting the MC for each DRB enables the settings of the MC withoutchanging the mapping relationship between the DRBs and the QoS flowswhich is set without performing the MC. This can avoid complexity in thecontrol over the MC.

FIGS. 43 to 45 illustrate an example sequence for setting the MC withthe SCG split bearer. FIGS. 43 to 45 are connected across locations ofborders BL4344 and BL4445. FIGS. 43 to 45 illustrate the use of the MgNBand two SgNBs (SgNB 1 and SgNB 2). FIGS. 43 to 45 illustrate a methodfor initially setting the SCG bearer and then changing the setting tothe SCG split bearer, similarly to the method disclosed in the eighthembodiment. Since the sequence illustrated in FIGS. 43 to 45 includesthe same steps as those of the sequences illustrated in FIGS. 33 to 35and FIGS. 38 to 40 , the same step numbers are applied to the same Stepsand the common description thereof is omitted.

In Step ST4301, the MgNB determines whether to set the DC to the UE, andfirst determines to set the DC with the SCG bearer to the UE.Alternatively, the MgNB may determine whether to set the DC with the SCGbearer to the UE. In Steps ST5501 and ST5503, Steps ST5505 to ST5507,Steps ST4302 and ST4303, Steps ST4207 and ST4208, and Steps ST5201 toST5212, the UE, the MgNB, the SgNB 1, the UPF, and AMF/SMF set the DCwith the SCG bearer.

In Step ST6501, the MgNB determines to set the MC using the SCG splitbearer with the SgNB 1 and the SgNB 2 to the UE. Assume that the SgNB 1is the P-SgNB and the SgNB 2 is another SgNB. In Step ST6502, the MgNBnotifies the SgNB 1 of a request for additionally setting the SgNB forthe SCG split bearer. The MgNB includes, in the notification,information to be included in the request for setting the SCG splitbearer to be notified from the MgNB to the SgNB, which is disclosed inthe eighth embodiment, to notify the information.

Upon receipt of the notification of the information in Step ST6502, theSgNB 1 notifies the SgNB 2 of the request for additionally setting theSgNB for the SCG split bearer in Step ST6503. The SgNB 1 includes, inthe notification, information to be included in the request for settingthe SCG split bearer to be notified from the P-SgNB to the other SgNBsfor the SCG split bearer, which is disclosed in the eighth embodiment,to notify the information.

Upon receipt of the information in Step ST6503, the SgNB 2 sets the SCGconfiguration and the DRB configuration to its own SgNB, and notifiesthe SgNB 1 functioning as the P-SgNB of a response to the request foradditionally setting the SgNB for the SCG split bearer in Step ST6504.Here, the SgNB 2 notifies the acknowledgement. The response shouldinclude information on the SCG configuration and the DRB configurationthat are set by its own SgNB.

Upon receipt of the information in Step ST6504, the SgNB 1 sets the SCGconfiguration and the DRB configuration to its own SgNB. In Step ST6505,the SgNB 1 notifies the MgNB of information on the SCG configuration andthe DRB configuration that are set by its own P-SgNB and on the SCGconfiguration and the DRB configuration that are set by another SgNB(SgNB 2).

In Step ST6506, the MgNB notifies the UE of the settings of the MC withthe SCG split bearer. The settings of the MC should include theinformation on the SCG configuration and the DRB configuration that areset by its own P-SgNB and on the SCG configuration and the DRBconfiguration that are set by the other SgNB. The MgNB may give thisnotification via the signaling for the RRC connection reconfiguration.For example, the method for notifying the DRB configuration from theMgNB to the UE, which is disclosed in the sixth embodiment, should beapplied to this notification. The UE can set the DRB configuration setto each of the SgNBs.

The UE makes settings of communication with the SgNB 1 and the SgNB 2using the settings of the MC with the SCG split bearer. In Step ST6507,the UE notifies the MgNB of completion of the settings. The UE may givethis notification via the signaling for the RRC connectionreconfiguration complete notification. In Step ST6508, the MgNB notifiesthe SgNB 1 of completion of the settings of the MC with the SCG splitbearer. In Step ST6509, the SgNB 1 notifies the SgNB 2 of completion ofthe settings of the MC with the SCG split bearer.

In Step ST6214, the UE performs the RA procedure with the SgNB 2 tosynchronize with the SgNB 2. This enables the UE to communicate with theSgNB 2. Consequently, the UE, the SgNB 1, the SgNB 2, and the UPFperform data communication with the MC using the SCG split bearer. Inother words, the UE, the MgNB, the SgNB 1, the SgNB 2, and the UPFperform data communication using the MC with the SCG split bearerbecause the UE and the MgNB perform communication for setting the MCwhich is independent of the DRB.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodmay be applied to the P-SgNB and the other SgNBs. When the MgNB isconfigured as a replacement for one of the other SgNBs, the method maybe applied to the P-SgNB, the MgNB, and the other SgNBs.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method may be applied to the P-SgNBand the other SgNBs. When the MgNB is configured as a replacement forone of the other SgNBs, the method may be applied to the P-SgNB, theMgNB, and the other SgNBs.

These methods can set the MC with the SCG split bearer to the UE foreach DRB even when the high-level NW is the NG-CN, which increases thethroughput.

Another method for setting the MC with the SCG split bearer isdisclosed. The MC is set for each QoS flow. The MC with the SCG splitbearer is set for each QoS flow. When the MC with the SCG bearer is setfor each QoS flow, the first modification of the seventh embodimentdescribes the occurrence of mainly one problem in addition to theproblems in setting the MC for each DRB. The problem is failing tonormally reorder the pieces of data of the QoS flows to which the MC isset. The SCG split bearer also causes this problem.

To solve such a problem, the method disclosed in the first modificationof the seventh embodiment should be appropriately applied thereto. Forexample, the DRB for the QoS flow on which the MC is performed isadditionally set, and the QoS flow on which the MC is performed ismapped to the additionally set DRB. Through setting the MC to theadditionally set DRB, the MC can be set to the QoS flow mapped to theDRB. This can set the MC for each QoS flow.

FIG. 46 is a conceptual diagram illustrating a dataflow when the MC withthe SCG split bearer is set for each QoS flow. Assume that the mappingrelationship between the QoS flows and the DRBs before the MC is set isthe one illustrated in FIG. 21 . Assume a DRB on which the MC isperformed as the DRB 1. The QoS flow 1 and the QoS flow 2 are mapped tothe DRB 1.

As illustrated in FIG. 46 , the MgNB additionally sets a PDU sessiontunnel to the SgNB 1 to be connected to the high-level NW in order toset the MC with the SCG bearer to the QoS flow 1 in the DRB 1. The PDUsession tunnel should be additionally set between the high-level NW andthe SgNB 1 (P-SgNB). The PDU session tunnel need not be additionally setbetween the other SgNBs (SgNB 2, SgNB 3) and the high-level NW.

The QoS flow 1 to which the MC is set is communicated through the addedPDU session tunnel. The packet data which the high-level NW maps to theQoS flow 1 is communicated through the added PDU session tunnel.

The data mapped to the QoS flow 1 is transferred to the New AS sublayerof the P-SgNB, and mapped to a DRBY 2 in the New AS sublayer. Thisenables the P-SgNB to process the QoS flow 1 to which the MC is set.

The PDCP of the P-SgNB splits and routes the data of the QoS flow 1mapped to the DRB 2, into its own P-SgNB and the other SgNBs. Similarlyin the downlink, the PDCP splits and routes the data of the QoS flow 1mapped to the DRBY 2 in the New AS sublayer of the UE into the RLCs forthe P-SgNB and the other SgNBs as the uplink data.

In the P-SgNB, the PDCP reorders the pieces of data from the P-SgNB andthe other SgNBs using the SNs. The New AS layer separates the pieces ofdata according to the QoS flow identifiers for each of the QoS flows,and then transfers the pieces of separated data to the high-level NW.

On the other hand, the MC is not performed on the QoS flow 2 in the DRB1, and the QoS flow 2 is communicated on the MgNB side. The MgNBmaintains, on the MgNB side, the DRB in the DRB 1 for the QoS flow 2.The MgNB may reconfigure the DRB 1. The MgNB should, for example,reconfigure the DRB configuration appropriate for the QoS flow 2 afterthe MC is set.

FIG. 46 illustrates the use of the same setting as that of the DRB 1 setby the MgNB. FIG. 46 illustrates the use of the DRB identifier (DRB 1)identical to that set by the MgNB.

The QoS flow 2 is communicated through the PDU session tunnelestablished between the high-level NW and the MgNB before the MC is set.The data which the high-level NW maps to the QoS flow 2 is transferredto the New AS sublayer of the MgNB, and then mapped to the DRB 1 in theNew AS sublayer. This enables the MgNB to process the QoS flow 2 towhich the MC is not set.

Not the DRB 1 or the DRBY 2 set in the downlink but a default DRB may beused in the uplink. When not the DRBY 2 but the default DRB is used, thePDCP in the UE splits and routes the data of the QoS flow 1 using thedefault DRB, into the RLCs for the P-SgNB and the other SgNBs.

When not the DRB 1 but the default DRB is used, the PDCP, the RLC, theMAC, and the PHY for the MgNB in the UE process the data of the QoS flow2 using the default DRB.

The MgNB should notify the UE of the reconfigured DRB configuration. TheUE can reconfigure the DRB configuration set on the MgNB side. The MgNBmay notify the configuration of the SgNB on which the MC is performed,and the DRB configuration set to each SgNB. For example, the method fornotifying the configuration of the DRB from the MgNB to the UE, which isdisclosed in the sixth embodiment, should be applied to thisnotification. The UE can set the DRB configuration set to each SgNB. Thesame applies to the uplink data. This can implement the MC for each QoSflow.

FIGS. 26 and 27 should be applied to the sequence for setting the MCwith the SCG split bearer for each QoS flow. Steps ST4902 to ST4913should be performed for additionally setting the DRB for the QoS flow onwhich the MC is performed. The DRB for the QoS flow on which the MC isperformed is additionally set, and the QoS flow on which the MC isperformed is mapped to the additionally set DRB. Through setting the MCto the additionally set DRB, the MC can be set to the QoS flow mapped tothe DRB.

In Step ST4914, the MgNB starts the MC setting with the SCG split beareras the DRB that has been additionally set for the QoS flow on which theMC is performed. In Step ST4915, the MgNB, the SgNB 1 and the SgNB 2 tobe used for the MC, the AMF/SMF, the UPF, and the UE mutually performthe MC setup processing using the SCG split bearer. FIGS. 43 to 45should be applied to this MC setup processing.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodshould be applied to the P-SgNB and the other SgNBs to each of which theMC is set for each QoS flow. When the MgNB is configured as areplacement for one of the other SgNBs, the method may be applied to theP-SgNB, the MgNB, and the other SgNBs.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method should be applied to theP-SgNB and the other SgNBs to each of which the MC is set for each QoSflow. When the MgNB is configured as a replacement for one of the otherSgNBs, the method may be applied to the P-SgNB, the MgNB, and the otherSgNBs. The SR or the BSR for each QoS flow may be provided and notifiedfrom the UE to the base station side.

This enables the MC with the SCG split bearer when the high-level NW isthe NG-CN. The MgNB can set the MC with the SCG split bearer to the UE.The UE can perform the MC through connecting with a plurality of SgNBsfor the MC.

The MgNB can perform the MC with the SCG split bearer on the UE for eachQoS flow. Since the MC can be performed for each QoS flow, the MC can becontrolled with QoS precision finer than that of the MC for each bearer.

The base stations to be split off from the P-SgNB for the MC may includethe MgNB. The MgNB may be set as a replacement for one of the otherSgNBs for the MC. The aforementioned method should be applied thereto.The use of the MgNB can reduce the number of the base stations to whichthe UE is connected.

The method disclosed in the first modification of the eighth embodimentcan configure the connection of one UE to a plurality of secondary basestations even when the high-level NW is the NG-CN. This can increase thethroughput of communication to be provided for the UE. Also, theconnection to a plurality of base stations can enhance the reliability.Moreover, since the MC with the SCG split bearer can be set, thehigh-level NW need not be connected to the plurality of secondary basestations. The complexity in the control between the high-level NW andthe base stations can be avoided.

The Ninth Embodiment

In 3GPP, introduction of a unified split bearer has been discussed asone method for performing the DC. Unifying the PDCP of the MeNB and thePDCPs of the SgNBs into a unified split bearer has been proposed.However, none discloses an architecture including the high-level NW or amethod for setting the MC with the unified split bearer.

Thus, for example, which base station the PDCP is provided to be used inand which base station the high-level NW is connected to are unknown.For another example, which base station the parameter of the PDCP isprovided in is unknown. The ninth embodiment discloses a method forsolving such problems.

The high-level NW is connected to a unified PDCP. The unified PDCP maybe referred to as a common PDCP. The high-level NW may be the MME or theS-GW. The S-GW may be connected to the common PDCP to be dedicated tothe U-plane. The common PDCP is provided for a DRB.

FIG. 47 illustrates an architecture of the MC. FIG. 47 illustrates thatthe high-level NW is an EPC, the master base station is a base stationin the LTE (eNB), and the secondary base stations are base stations inNR (gNBs). Although FIG. 47 illustrates the architecture on the basestation side, the architecture on the UE side is identical to that onthe base station side except for the high-level NW. One UE includes thecommon PDCP, and the RLCs, the MACs, and the PHYs for the MeNB and theSgNBs.

FIG. 47 illustrates the use of the unified split bearer. The high-levelNW is connected to the common PDCP, and the common PDCP is connected tothe MeNB and the SgNBs for the MC. The downlink data is transferred fromthe high-level NW to the common PDCP, and processed by the common PDCP.The PDCP assigns one serial sequence number (SN) to each data.

The data to which the common PDCP assigns the SN is split and routed tothe MeNB and the SgNBs for the MC. The pieces of data split and routedare transmitted to the MeNB and the SgNBs, processed by the RLCs, theMACs, and the PHYs, and transmitted to the UE.

The pieces of data received by the UE from the MeNB and the SgNBs areprocessed by the PHYs, the MACs, and the RLCs for the MeNB and theSgNBs, and then transferred to the common PDCP. The common PDCP reordersthe pieces of data transferred from those for the MeNB and the SgNBs,based on the SNs assigned thereto, and then transfers the pieces of datato the upper layer.

The common PDCP in the UE processes the pieces of data from the upperlayer as the uplink data. Similarly in the downlink, the common PDCPassigns one serial sequence number (SN) to each data in the uplink. Thedata to which the SN is assigned is split into the RLCs for the MeNB andthe SgNBs to be transferred. The pieces of transferred data areprocessed by the RLCs, the MACs, and the PHYs for the MeNB and theSgNBs, and then transmitted to the MeNB and the SgNBs.

The pieces of data received by the MeNB and the SgNBs from the UE areprocessed by the PHYs, the MACs, and the RLCs for the MeNB and theSgNBs, and then transferred to the common PDCP. The common PDCP reordersthe pieces of data based on the SNs assigned thereto, and then transfersthe pieces of data to the high-level NW.

The common PDCP may be provided in one independent node. Alternatively,the common PDCP may be provided in a base station. For example, thecommon PDCP may be provided in the MeNB or the SgNB. Alternatively, thecommon PDCP may be provided in the high-level NW. The common PDCP hasonly to include a PDCP function uniform between the base stations to beconnected. The common PDCP may be provided in any node.

Examples of the parameter to be used in the PDCP include a parameterrelated to header compression, and a cipher-related parameter. Theparameter of the common PDCP should be a parameter dedicated to thecommon PDCP. The MeNB should set the parameter. The MeNB notifies the UEof the parameter of the common PDCP. The MeNB may give this notificationvia the RRC signaling. The MeNB sets the parameter of the common PDCP,and then notifies a node with the common PDCP of the parameter.

The UE sets the parameter notified from the MeNB as the parameter usedin the common PDCP to perform processes in the common PDCP. The MeNB maynotify the UE to set the MC using the common PDCP. The MeNB may givethis notification via the RRC signaling. This notification may includethe parameter for the common PDCP.

Although disclosed is that the MeNB sets the parameter, the SgNB may setthe parameter. Alternatively, the high-level NW may set the parameter.The node with the common PDCP function may set the parameter. The nodethat has set the parameter notifies the MeNB of the parameter. The MeNBshould notify the UE of the parameter.

The use of the parameter dedicated to the common PDCP can make adistinction from the PDCP parameters of the MeNB and the SgNB.

As an alternative method, the parameter to be used in the common PDCPmay be a parameter of the PDCP set by the MeNB. The parameter may be aparameter of the PDCP that is configured by the MeNB before setting theMC. The MeNB notifies the UE of the parameter of the common PDCP. TheMeNB notifies the parameter to the node with the common PDCP.

The common PDCP may be a PDCP before the MC is set. The PDCP before theMC is set may be set to the common PDCP by setting the MC. In such acase, the use of a PDCP parameter before the MC is set as the parameterfor the common PDCP can ensure the continuity in the PDCP parameter.This makes the parameter setting and the signaling for the common PDCPunnecessary.

As an alternative method, the parameter to be used in the PDCP may be aparameter of the PDCP of the SgNB. The parameter may be a parameter ofthe PDCP that is configured by the SgNB by setting the MC. The SgNBnotifies the UE of the parameter of the common PDCP. The SgNB may notifythe UE of the parameter through the MeNB.

The common PDCP may be provided in the SgNB to be connected to thehigh-level NW. For example, when the SCG bearer is changed to theunified split bearer, the use of the parameter of the PDCP of the SgNBas the parameter for the common PDCP can make the parameter setting andthe signaling for the common PDCP unnecessary.

Which one of the methods for setting the common PDCP is used may beconfigurable. The high-level NW may determine which method is used, andnotify the method to a node or a base station that includes the commonPDCP. Alternatively, the MeNB may determine which method is used, andnotify the method to a node or a base station that includes the commonPDCP. The MeNB may notify the UE of the setting method. The MeNB maynotify the UE of the setting method as well as information on the nodeor the base station that includes the common PDCP.

An indicator for determining which method is used may be, for example,capability for processing the PDCP by each base station. The PDCP of abase station with high capability for processing the PDCP is used as thecommon PDCP. This can suppress, for example, reduction in the processingspeed in an overloaded state caused by the processing of the commonPDCP, and an abnormal end of the processing.

The methods disclosed in the sixth and eighth embodiments should beappropriately applied to the method for setting the MC with the unifiedsplit bearer.

When a parameter is set as the parameter for the common PDCP, the PDCPbefore the MC is set differs from the PDCP after the MC is set. Theprocessing on the DRB to which the MC is set is changed from processingperformed by the PDCP of the MeNB to processing performed by the commonPDCP. The method for changing into the SCG split bearer, which isdisclosed in the eighth embodiment, should be appropriately applied tothe changing method. The common PDCP should be used to replace the PDCPof the P-SgNB. The setting of each SgNB should be used to replace thesettings of the other SgNB s. One of the other SgNBs may be the MeNB.

When the MeNB exists as one of the SgNBs, the settings of the RLC orlower in the MeNB may be identical to those before the MC is set. TheDRB configuration before the MC is set can gain a desired QoS evenwithout any change.

The SN status of the PDCP of the MeNB and data should be transferred asthe data forwarding method when the MC is set. The method for changinginto the SCG split bearer, which is disclosed in the eighth embodiment,should be appropriately applied as the transferring method. The commonPDCP should be used to replace the PDCP of the P-SgNB.

As a method for the MeNB to set the MC to the UE, the MeNB notifies theUE of the setting of the common PDCP and the setting of each SgNB. Themethod for changing into the split bearer, which is disclosed in theeighth embodiment, should be appropriately applied as the settingmethod. This can set the MC with the unified split bearer to the UE.

When the PDCP parameter of the MeNB is used as the parameter of thecommon PDCP, the PDCP parameter before the MC is set is identical to thePDCP parameter after the MC is set. The method for changing into the MCGsplit bearer, which is disclosed in the sixth embodiment, should beappropriately applied to the method for setting the MC. As a method forthe MeNB to set the MC to the UE, the MeNB notifies the UE of thesettings of the MC with the MCG split bearer.

When the PDCP parameter of the SgNB is used as the parameter of thecommon PDCP, the setting of the SCG split bearer disclosed in the eighthembodiment should be appropriately applied. The MeNB determines of whichSgNB the PDCP parameter is used. The disclosed method on the SCG splitbearer should be appropriately applied to the method for determining theSgNB. The method for determining the P-SgNB should be applied thereto.

The processing on the DRB to which the MC is set should be changed fromprocessing performed by the PDCP of the MeNB to processing performed bythe PDCP of the SgNB. The method for changing into the SCG split bearer,which is disclosed in the eighth embodiment, should be appropriatelyapplied as the changing method. A predetermined SgNB should beappropriately used to replace the P-SgNB. The setting of each SgNBshould be appropriately used to replace the settings of the other SgNBs.One of the other SgNB s may be the MeNB.

The SN status of the PDCP of the MeNB and data should be transferred asthe data forwarding method. The method for changing into the SCG splitbearer should be appropriately applied as the transferring method. ThePDCP of a predetermined SgNB should be appropriately used to replace thePDCP of the P-SgNB.

As a method for the MeNB to set the MC to the UE, the MeNB notifies theUE of the setting of the P-SgNB and the settings of the other SgNBs. Themethod for changing into the SCG split bearer should be appropriatelyapplied as the setting method.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodmay be applied to the gNB or the eNB to which the MC is set.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method may be applied to the gNB orthe eNB to which the MC is set.

This saves distinguishing the state of the MC with the MCG split bearerfrom the state of the MC with the SCG split bearer.

The eNBs that are base stations in the LTE may be used as base stationsfor the MC. The base stations may include an eNB and a gNB. Since thebase stations for the MC do not use the New AS sublayer, the eNBs can beused as the base stations.

The method disclosed in the ninth embodiment can configure theconnection of one UE to a plurality of base stations. This can increasethe throughput of communication to be provided for the UE. Moreover, theconnection to a plurality of base stations can enhance the reliability.Since the MC with the unified split bearer can be set, the split bearercan be controlled and managed in one state. Thus, the complexity in thecontrol and management with the MC can be avoided.

The First Modification of the Ninth Embodiment

The first modification discloses a method for setting the MC with theunified split bearer when the high-level NW is an NG-CN. In the ninthembodiment, the common PDCP is the PDCP obtained by unifying the PDCP ofthe MeNB and the PDCPs of the SgNBs. Since the high-level NW is theNG-CN in the first modification, the common PDCP is the PDCP obtained byunifying the PDCPs of the SgNBs, and the PDCP of the MgNB or the MeNBthat can be connected to the NG-CN.

The New AS sublayer is provided between the common PDCP and the NG-CN.The high-level NW is connected to the New AS sublayer, and the New ASsublayer is connected to the common PDCP. The high-level NW may be theAMF or the UPF. The UPF may be connected to the New AS sublayer to bededicated to the U-plane.

The New AS sublayer maps a QoS flow from the high-level NW to a DRBaccording to the QoS flow identifier. The common PDCP is provided forthe DRB.

FIG. 48 illustrates an architecture of the MC. FIG. 48 illustrates thatthe high-level NW is the NG-CN, the master base station is a basestation in NR (gNB), and the secondary base stations are base stationsin NR (gNBs). Although FIG. 48 illustrates the architecture on the basestation side, the architecture on the UE side is identical to that onthe base station side except for the high-level NW. One UE includes theNew AS sublayer, the common PDCP, and the RLCs, the MACs, and the PHYsfor the MgNB and the SgNBs.

FIG. 48 illustrates the use of the unified split bearer. The high-levelNW is connected to the New AS sublayer, and the New AS sublayer isconnected to the common PDCP. The common PDCP is connected to the MgNBand the SgNBs for the MC. The high-level NW maps the downlink data tothe QoS flow, and then transfers the downlink data to the New ASsublayer.

The New AS sublayer maps the downlink data from the QoS flow to a DRB,and then transfers the downlink data to the common PDCP configured withthe DRB. Then, the common PDCP processes the downlink data. The PDCPassigns one serial sequence number (SN) to each data.

The data to which the common PDCP assigns the SN is split and routed tothe MgNB and the SgNBs for the MC. The pieces of data split and routedare transmitted to the MgNB and the SgNBs, then processed by the RLCs,the MACs, and the PHYs, and then transmitted to the UE.

The pieces of data received by the UE from the MgNB and the SgNBs areprocessed by the PHYs, the MACs, and the RLCs for the MgNB and theSgNBs, and then transferred to the common PDCP. The common PDCP reordersthe pieces of data transferred from those for the MgNB and the SgNBs,based on the SNs assigned thereto, and then transfers the pieces of datato the New AS sublayer. The New AS sublayer separates the pieces of dataaccording to the QoS flow identifiers for each of the QoS flows, andthen transfers the pieces of separated data to the upper layer.

As for the uplink data, the New AS layer of the UE maps the pieces ofdata from the upper layer, from the QoS flow to the DRB. The pieces ofdata mapped to the DRB are transferred to the common PDCP, and processedby the common PDCP. Similarly in the downlink, the common PDCP assignsone serial sequence number (SN) to each data in the uplink.

The data to which the SN is assigned is split into the RLCs for the MgNBand the SgNBs to be transferred. The pieces of transferred data areprocessed by the RLCs, the MACs, and the PHYs for the MgNB and theSgNBs, and then transmitted to the MgNB and the SgNBs.

The pieces of data received by the MgNB and the SgNBs from the UE areprocessed by the PHYs, the MACs, and the RLCs for the MgNB and theSgNBs, and then transferred to the common PDCP. The common PDCP reordersthe pieces of data based on the SNs assigned thereto, and then transfersthe pieces of data to the New AS sublayer. The New AS sublayer separatesthe pieces of data according to the QoS flow identifiers for each of theQoS flows, and then transfers the pieces of separated data to thehigh-level NW.

The common PDCP may be provided in one independent node, and the New ASsublayer may be provided in another independent node. Alternatively, thecommon PDCP and the New AS sublayer may be provided in the same node.Such provision in the same node facilitates transfer from the New ASsublayer to the PDCP. The common PDCP and the New AS sublayer may beprovided in a base station. For example, the common PDCP and the New ASsublayer may be provided in the MgNB or the SgNB. Alternatively, thecommon PDCP and the New AS sublayer may be provided in the high-levelNW.

The method disclosed in the ninth embodiment should be appropriatelyapplied to the PDCP parameter of the common PDCP. The MgNB may replacethe MeNB.

The methods disclosed in the first modifications of the sixth and eighthembodiments should be appropriately applied to the method for settingthe MC with the unified split bearer, similarly to the settings of theMC for each DRB and the settings of the MC for each QoS flow in theninth embodiment.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the data split method with the MC in the uplink. The methodmay be applied to the gNB or the eNB to which the MC is set.

The method disclosed in the sixth embodiment should be appropriatelyapplied to the method for starting transmission of the uplink data fromthe UE to the base station side. The method may be applied to the gNB orthe eNB to which the MC is set.

This saves distinguishing the state of the MC with the MCG split bearerfrom the state of the MC with the SCG split bearer even when thehigh-level NW is the NG-CN. The split bearer can be controlled andmanaged in one state. Thus, the complexity in the control and managementwith the MC can be avoided.

When a parameter set as a parameter dedicated to the common PDCP is usedin the common PDCP, each SgNB or the MgNB configures the layers lowerthan the RLC. Thus, when the gNB and the eNB have the same layers lowerthan the RLC layers, there is no need to distinguish between the gNB andthe eNB.

When base stations do not include the common PDCP, the eNBs that arebase stations in the LTE may be used as the base stations for the MC.The base stations may be eNBs and gNBs. Since the base stations for theMC do not use the New AS sublayer, the eNBs can be used as the basestations.

Alternatively, when a base station includes the common PDCP along withthe New AS sublayer, the eNBs that are base stations in the LTE may beused as base stations for the MC, except for the base station includingthe common PDCP and the New AS sublayer. The base stations may includean eNB and a gNB. Since the base stations for the MC do not use the NewAS sublayer, the eNBs can be used as the base stations.

Coexistence of the gNB and the eNB as the base stations to be used forthe MC enables flexible setting of the base stations to be used for theMC. Thus, the MC can be set using appropriate base stations accordingto, for example, positions of the base stations and situations such asload states of the base stations, which increases the throughput.

The method disclosed in the first modification of the ninth embodimentcan configure the connection of one UE to a plurality of base stationseven when the high-level NW is the NG-CN. This can increase thethroughput of communication to be provided for the UE. Moreover, theconnection to a plurality of base stations can enhance the reliability.Since the MC with the unified split bearer can be set, the split bearercan be controlled and managed in one state. Thus, the complexity in thecontrol and management with the MC can be avoided.

The Tenth Embodiment

The sixth, seventh, eighth, and ninth embodiments disclose the methodsfor configuring the MC. The tenth embodiment discloses modifying andreleasing a MC configuration.

The MeNB may activate modifying the MC configuration. The modificationof the MC configuration may be, for example, a modification of theconfiguration in the SgNB (an SgNB modification). The modification ofthe configuration may mean, for example, addition, modification, andremoval of a bearer that passes through the SgNB. The addition of thebearer that passes through the SgNB may mean a setting of a new bearer,or addition of the SgNB as a branch destination of the existing bearer.The same may apply to removal of a bearer.

The MeNB may notify the SgNB of an SgNB modification request. The MeNBmay notify the SgNB modification request only to an SgNB whoseconfiguration is to be modified among the SgNBs that configure the MC.The MeNB may notify the SgNB modification request through the Xninterface.

The SgNB modification request may include an identifier of a bearer. Theidentifier of the bearer may be an identifier of a bearer to be added,modified, or removed. The SgNB modification request may include a typeof the bearer. The type of the bearer may be, for example, the MCG splitbearer, the MCG bearer, the SCG split bearer, the SCG bearer, or theunified bearer described in the ninth embodiment. The type of the bearershould be a type after modification. This can flexibly modify the typeof the bearer.

The SgNB modification request may include the setting of a bearer. Thesetting of the bearer may be, for example, a parameter on the QoS orparameters on protocols such as the RLC and the MAC. The setting canflexibly change the setting of the bearer that passes through the SgNB.

Alternatively, the SgNB modification request may include informationnecessary for routing from the SgNB to the other SgNBs. The informationmay be the one described in the eighth embodiment. Alternatively, theSgNB modification request may include information indicating whether therouting is performed. Whether the routing from the SgNB to the otherSgNBs is performed can be flexibly switched.

The SgNB may transmit an SgNB modification request acknowledgement tothe MeNB. The SgNB may transmit the SgNB modification requestacknowledgement after receiving the SgNB modification request.

The SgNB modification request acknowledgement may include an identifierof a bearer. The identifier of the bearer may be an identifier of abearer to be added, modified, or removed. Alternatively, the SgNBmodification request acknowledgement may include the AS setting from theSgNB to the UE, for example, the RRC parameter and the setting for theRA procedure.

For example, the SgNB may transmit an SgNB modification requestrejection to the MeNB. The SgNB may transmit the SgNB modificationrequest rejection as a rejection response to the SgNB modificationrequest transmitted from the MeNB to the SgNB. Information included inthe SgNB modification request rejection may be identical to thataccording to the second embodiment.

The MeNB may notify the UE to modify the MC configuration. In responseto the notification, the UE may modify the MC configuration. The MeNBnotifies the UE of the SCG setting as a modification of the MCconfiguration. The MeNB may notify the UE of the SCG setting afterreceiving the SgNB modification request acknowledgement. The MeNB maygive the notification via the RRC signaling. Similarly to the sixthembodiment, the RRC connection reconfiguration(RRCConnectionReconfiguration) may be used as the RRC signaling.Similarly to the sixth embodiment, the MeNB may give the notificationby, for example, including an SCG configuration in SCG-ConfigPartSCG inthe signaling. Alternatively, the notification may include aconfiguration of a bearer to which the MC is set. Examples of theconfiguration of the bearer include a bearer identifier, and the ASsetting for the bearer.

The RRC connection reconfiguration may include information on a bearerthat releases the SCG. The bearer that releases the SCG may be, forexample, a bearer that releases the SCG from a branch destination of itsown bearer. The number of pieces of the information on the bearer may beone or more. A list including the pieces of information on the bearermay be provided. The information on the bearer may be included in, forexample, the SCG-ConfigPartSCG described in the sixth embodiment. Thesame may apply to the list. For example, the list may be newly providedin the SCG-ConfigPartSCG (e.g., drb-ToReleaseListSCG). For example, abearer to be used as a branch destination can be promptly changed foreach SCG.

Alternatively, information on one or more radio bearers to which the MCis set may be included in the RRC connection reconfiguration. Similarlyto the sixth embodiment, the radio bearer information may include theinformation on the SCG to be used by the radio bearers. The radio bearerinformation may be identical to that described in the sixth embodiment.Consequently, the radio bearer for performing the MC can be easilychanged.

Alternatively, the radio bearer information may include information onthe SCG to be released from the radio bearer. The number of pieces ofthe information on the SCG may be one or more. A list including thepieces of information on the SCG may be provided. Consequently, the UEcan promptly change the SCG at a branch destination for each bearer.

The RRC connection reconfiguration may include information on a bearerto be removed. The information may be, for example, an identifier of abearer. The number of the bearers to be removed may be one or more. Alist including information on the bearers to be removed may be provided.This can reduce the amount of signaling for removing the bearer.

The UE may notify the MeNB of a response to modification of the MCconfiguration. The UE may give the notification, for example, afterreceiving the RRC connection reconfiguration. The UE may give thenotification via the RRC signaling, for example, using the RRCconnection reconfiguration complete(RRCConnectionReconfigurationComplete) notification. The MeNB cansmoothly perform a process for modifying the MC configuration byreceiving the response to modification of the MC configuration from theUE.

The MeNB may transmit, to the SgNB, a notification indicating thecompletion of the modification of the MC configuration. The MeNB maygive the notification through the Xn interface. The MeNB may give thenotification after receiving the response to modification of the MCconfiguration from the UE. The MeNB may give the notification via, forexample, the SgNB reconfiguration complete notification. The informationincluded in the notification may be identical to that included in theSgNB modification request.

Similarly to the sixth embodiment, the MeNB may set, to the UE,modification of the MC configuration for each SCG. The sequence formodifying the MC configuration may be identical to, for example, thatillustrated in FIGS. 17 and 18 . Even upon occurrence of a failure inchanging the SgNB for the MC on the way, the MC can be performed whilesuccessful change in the SgNB for the MC until then is maintained.

Alternatively, the MC configuration can be modified collectively for theSCGs. The sequence for modifying the MC configuration may be identicalto, for example, that illustrated in FIGS. 19 and 20 . This can reducethe amount of signaling.

Alternatively, the MC configuration can be modified for each bearer orcollectively for the bearers. This can reduce the amount of signaling.

In the tenth embodiment, the SgNB may activate modifying the MCconfiguration.

The SgNB may transmit a SgNB modification required notification to theMeNB. Information included in the notification may be identical to thatincluded in the SgNB modification request acknowledgement.

The MeNB may transmit the SgNB modification refusal to the SgNB. TheMeNB may transmit the SgNB modification refusal as a refusal response tothe SgNB modification required notification transmitted from the SgNB tothe MeNB. Information included in the SgNB modification refusal may beidentical to that according to the second embodiment.

The MeNB may notify the UE to modify the MC configuration. The MeNB maynotify the UE after receiving the SgNB modification requirednotification from the SgNB. The MeNB may give the notification ofmodifying the MC configuration using, for example, the RRC connectionreconfiguration as previously described. Information included in thenotification of modifying the MC configuration may be identical to thatpreviously described.

The UE may give the MeNB the RRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification as previouslydescribed.

The MeNB may notify the SgNB of the SgNB modification confirmation. TheMeNB may give the notification through the interface between the basestations, for example, the Xn interface. Information included in thenotification may be identical to that included in the SgNB modificationrequest.

The method identical to that for modifying the MC configuration may beapplied to intra-MeNB handover (HO) involving SCG change in the MCconfiguration. The design complexity in the communication system can beavoided.

The sequence similar to that for modifying the MC configuration may beapplied to release of the SgNB in the MC configuration. The designcomplexity in the communication system can be avoided.

However, in the RRC signaling for the RRC connection reconfiguration,information on releasing the SCGs is limited to an identifier indicatingwhether to release the SCGs. As a result of releasing the SgNB through asequence similar to that for modifying the MC configuration, the UEcannot recognize which SCG is to be released and may malfunction.

Thus, the RRC connection reconfiguration may include information on theSCG to be released. The information on the SCG to be released may beidentical to that described in the sixth embodiment, for example, anidentifier of the SCG. The number of pieces of the information on theSCG to be released may be one or more. This can reduce the amount ofsignaling for releasing a plurality of SCGs. A new list includinginformation on the SCGs to be released may be provided.

Alternatively, all the SCGs configuring the MC may be released usinginformation on only the identifier indicating whether or not to releasethe SCGs. This can reduce the amount of signaling for collectivelyreleasing the SCGs.

Consequently, the MgNB can specify the SgNB to be released for the UE,which can prevent the UE from malfunctioning when the SCG is released.

The method described in the sixth embodiment may be combined with therelease of the SgNB, to be applied to change of the SgNB in the MCconfiguration. The design complexity in the communication system can beavoided.

The handover request described in 9.1.1.1 of Non-Patent Document 23(3GPP TS36.423 v14.3.0) may be combined with the release of the SgNB, tobe applied to the handover from the MeNB to the eNB (MeNB to eNB Change)in the MC configuration. The design complexity in the communicationsystem can be avoided.

The handover request described in 9.1.1.1 of Non-Patent Document 23(3GPP TS36.423 v14.3.0) may be combined with the method described in thesixth embodiment, to be applied to the handover from the eNB to the MeNB(eNB to MeNB Change) in the MC configuration. The design complexity inthe communication system can be avoided.

The handover request described in 9.1.1.1 of Non-Patent Document 23(3GPP TS36.423 v14.3.0) may be combined with the method described in thesixth embodiment and the release of the SgNB, to be applied to theinter-MeNB handover (HO) without SgNB change in the MC configuration.The design complexity in the communication system can be avoided.

However, since nothing but information on one SgNB can be notified viathe signaling for the handover request, the target MeNB cannot obtaininformation on SgNBs other than the one SgNB indicated by thenotification. As a result, a problem of failure in the MeNB handoverwithout SgNB change occurs in the MC.

Thus, the signaling for the handover request may include a plurality ofpieces of information on an SgNB.

Alternatively, the source MeNB may notify the target MeNB of thesignaling for the handover request a plurality of times. The source MeNBmay include information on different SgNBs in the notification given aplurality of times to notify the information.

The target MeNB may notify the source MeNB of the Handover RequestAcknowledgement described in 9.1.1.2 of Non-Patent Document 23 (3GPPTS36.423 v14.3.0). The target MeNB may transmit the Handover RequestAcknowledgement in response to each signaling for the handover request,or transmit the Handover Request Acknowledgement once upon receipt ofthe signaling for the handover request a plurality of times.

Consequently, the target MeNB can obtain information on a plurality ofSgNBs in the MC configuration. Thus, the MeNB handover without SgNBchange is possible in the MC.

Since the tenth embodiment enables the modification and release of theMC configuration, the optimal communication system can be builtaccording to a communication state of the whole system.

The First Modification of the Tenth Embodiment

The tenth embodiment may be applied to the MC configuration using theNew AS layer.

Similarly to the tenth embodiment, the MgNB may activate modifying theMC configuration. The modification of the MC configuration may be, forexample, modification of a configuration in a secondary base station (SNModification). The modification of the configuration may be, forexample, addition, modification, and removal of a bearer that passesthrough the secondary base station or addition, modification, andremoval of a QoS flow that passes through the secondary base station.

The MgNB may notify the secondary base station of a secondary basestation modification request (SN Modification Request). The MgNB maynotify the secondary base station modification request only to asecondary base station whose configuration is to be modified, amongsecondary base stations configuring the MC. The MgNB may notify thesecondary base station modification request through the Xn interface.

The secondary base station modification request may include the same asthose included in the SgNB modification request described in the tenthembodiment. The same advantages as those described in the tenthembodiment are given.

Alternatively, the secondary base station modification request mayinclude information indicating a QoS flow. The information may be, forexample, an identifier of the QoS flow. The information may be includedin, for example, information on a bearer through which the QoS flowpasses. This can set whether data is split into the secondary basestation for each QoS flow.

The secondary base station may transmit a secondary base stationmodification request acknowledgement (SN Modification RequestAcknowledge) to the MgNB. The secondary base station may transmit thesecondary base station modification request acknowledgement, similarlyto the SgNB modification request acknowledgement in the tenthembodiment.

The secondary base station modification request acknowledgement mayinclude the same as those included in the SgNB modification requestacknowledgement described in the tenth embodiment. The same advantagesas those described in the tenth embodiment are given.

Alternatively, the secondary base station modification requestacknowledgement may include information indicating a QoS flow. Theinformation may be, for example, an identifier of the QoS flow. Theinformation may be included in, for example, information on a bearerthrough which the QoS flow passes. This enables the MgNB to properlyperform control for each QoS flow.

The secondary base station may transmit a secondary base stationmodification request rejection (SN Modification Request Reject) to theMgNB. The secondary base station may transmit the secondary base stationmodification request rejection as a rejection response to the secondarybase station modification request transmitted from the MgNB to thesecondary base station. Information included in the secondary basestation modification request rejection may be identical to that includedin the SgNB modification rejection response described in the tenthembodiment. Alternatively, the information may include information on aQoS flow, for example, an identifier of the QoS flow. The QoS flow maybe a QoS flow that causes the secondary base station to reject therequest. This enables, for example, the MgNB to smoothly perform aprocess for changing the secondary base station per QoS flow.

Similarly to the tenth embodiment, the MgNB may notify the UE to modifythe MC configuration. In response to the notification, the UE may modifythe MC configuration. The MgNB may give the notification via the RRCsignaling, for example, using the RRC connection reconfiguration(RRCConnectionReconfiguration).

Information included in the notification may be identical to thataccording to the tenth embodiment. The same advantages as thosedescribed in the tenth embodiment are produced.

Alternatively, the notification of modifying the MC configuration, forexample, the RRC connection reconfiguration may include informationindicating a QoS flow. The notification may include, for example, anidentifier of the QoS flow as the information.

The notification may include, for example, information on a bearerthrough which the QoS flow passes, for example, the identifier of theQoS flow. The notification may include an identifier of the MCG and/orthe SCG as a split destination of the QoS flow. Thus, a base stationand/or a bearer as a split destination for each QoS flow from the MgNBto the UE can be flexibly set.

Alternatively, the notification of modifying the MC configuration, forexample, the RRC connection reconfiguration may include information on aQoS flow to be removed. The information may be, for example, anidentifier of the QoS flow. The number of QoS flows to be removed may beone or more. A list including information on the QoS flows to be removedmay be provided. This can reduce the amount of signaling for removingthe QoS flows.

Similarly to the tenth embodiment, the MgNB may set, to the UE, themodification of the MC configuration for each SCG. The MgNB may set abearer to be used for each SCG. The MgNB may set a QoS flow for eachbearer or for each SCG. For example, in the signaling for the RRCconnection reconfiguration, information on the setting of the SCG mayinclude information on a bearer to be used. The information on thebearer may include information on a QoS to be used. The information onthe setting of the SCG may include information on a QoS flow to be used.The setting for each SCG may be collectively performed for the SCGs.This can reduce the amount of signaling for changing the SCG.

Alternatively, the MgNB may set the modification of the MC configurationto the UE for each bearer similarly to the tenth embodiment. Forexample, the MgNB may set the QoS flow to be used for each bearer. TheMgNB may set the MCG and/or the SCG for each QoS flow or for eachbearer. For example, in the signaling for the RRC connectionreconfiguration, information on the setting of the bearer may includeinformation on a QoS flow to be used. The information on the QoS flow orthe information on the setting of the bearer may include information onthe MCG and/or the SCG to be used. The setting for each bearer may becollectively performed for the bearers. This can reduce the amount ofsignaling for changing the bearer.

Alternatively, the MgNB may set the modification of the MC configurationto the UE for each QoS flow. For example, the MgNB may set a bearer tobe used for each QoS flow. The MgNB may set the MCG and/or the SCG foreach bearer. Alternatively, the MgNB may set the MCG and/or the SCG foreach QoS flow. The MgNB may set a bearer for each MCG and/or for eachSCG. The MgNB may set the MCG and/or the SCG for each bearer. Forexample, in the signaling for the RRC connection reconfiguration,information on the setting of the QoS flow may include information on abearer to be used. The information on the bearer may include informationon the MCG and/or the SCG to be used. Alternatively, the information onthe setting of the QoS flow may include the information on the MCGand/or the SCG to be used. The information on the MCG and/or the SCG mayinclude the information on a bearer to be used. The setting for each QoSflow may be collectively performed for the QoS flows. This can reducethe amount of signaling for changing the QoS flow.

The UE may notify the MgNB of a response to modification of the MCconfiguration. Similarly to the tenth embodiment, the UE may give thenotification using the RRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification. The same advantagesas those described in the tenth embodiment are produced.

The MgNB may transmit, to the secondary base station, a notificationindicating the completion of the modification of the MC configuration.The MgNB may give the notification, for example, using the secondarybase station reconfiguration complete (SN Reconfiguration Complete)notification. The MgNB may transmit the notification in the same manneras the SgNB reconfiguration completion notification described in thetenth embodiment. The same advantages as those described in the tenthembodiment are produced.

Similarly to the tenth embodiment, the MgNB may set, to the UE, themodification of the MC configuration for each SCG. The sequence formodifying the MC configuration may be identical to, for example, thatillustrated in FIGS. 17 and 18 . Even upon occurrence of a failure inchanging the SgNB for the MC on the way, the MC can be performed whilesuccessful change in the SgNB for the MC until then is maintained.

Alternatively, the MC configuration may be collectively modified for theSCGs. The sequence for modifying the MC configuration may be identicalto, for example, that illustrated in FIGS. 19 and 20 . This can reducethe amount of signaling.

Alternatively, modification of the MC configuration may be set for eachbearer or in a batch of the bearers. This can reduce the amount ofsignaling.

Alternatively, the modification of the MC configuration may be set foreach QoS flow or in a batch of the QoS flows. This can reduce the amountof signaling.

Alternatively, the secondary base station may activate modifying the MCconfiguration similarly to the tenth embodiment.

The secondary base station may transmit a secondary base stationmodification required (SN Modification Required) notification to theMgNB. Information included in the notification may be identical to thatincluded in the SgNB modification request acknowledgement described inthe tenth embodiment.

The MgNB may transmit a secondary base station modification refusal (SNModification Refuse) to the secondary base station. The MgNB maytransmit the secondary base station modification refusal as a refusalresponse to the secondary base station modification requirednotification transmitted from the secondary base station to the MgNB.

Information included in the secondary base station modification refusalmay be identical to that included in the SgNB modification refusaldescribed in the tenth embodiment. Alternatively, the information mayinclude information on a QoS flow, for example, an identifier of the QoSflow. The QoS flow may be a QoS flow that causes the MgNB to refuse therequest. This enables, for example, the secondary base station tosmoothly perform the process for changing the secondary base station perQoS flow.

The MgNB may notify the UE to modify the MC configuration. The MgNB maynotify the UE after receiving the secondary base station modificationrequired notification from the secondary base station. The MgNB may givethe notification of modifying the MC configuration using, for example,the RRC connection reconfiguration as previously described. Informationincluded in the notification of modifying the MC configuration may beidentical to that previously described.

The UE may give the MgNB the RRC connection reconfiguration complete(RRCConnectionReconfigurationComplete) notification as previouslydescribed.

The MgNB may notify the secondary base station of a secondary basestation modification confirmation (SN Modification Confirm). The MgNBmay give the notification through the interface between the basestations, for example, the Xn interface. Information included in thenotification may be identical to that included in the secondary basestation modification request (SN Modification Request).

The method identical to that for modifying the MC configuration usingthe New AS layer may be applied to intra-MgNB (MN) handover (HO)involving SCG change, in the MC configuration using the New AS layer.The design complexity in the communication system can be avoided.

The sequence identical to that for releasing the SgNB (SgNB Release),which is described in the tenth embodiment, may be applied to release ofthe secondary base station (SN Release) in the MC configuration usingthe New AS layer. The design complexity in the communication system canbe avoided.

The method described in the first modification of the sixth embodimentmay be combined with the release of the secondary base station (SNRelease), to be applied to change of the secondary base station (Changeof SN) in the MC configuration using the New AS layer. The designcomplexity in the communication system can be avoided.

The handover request described in 9.1.1.1 of Non-Patent Document 29(3GPP TS38.423 v0.1.1) may be combined with the release of the secondarybase station (SN Release), to be applied to the handover from the MgNBto the gNB (MN to gNB Change) in the MC configuration using the New ASlayer. The design complexity in the communication system can be avoided.

The handover request described in 9.1.1.1 of Non-Patent Document 29(3GPP TS38.423 v0.1.1) may be combined with the method described in thefirst modification of the sixth embodiment, to be applied to thehandover from the gNB to the MgNB (gNB to MN Change) in the MCconfiguration using the New AS layer. The design complexity in thecommunication system can be avoided.

The sequence identical to that for the inter-MeNB handover (HO) withoutSgNB change in the MC configuration, which is described in the tenthembodiment, may be applied to the inter-MgNB handover (HO) withoutsecondary base station (SN) change in the MC configuration using the NewAS layer. The design complexity in the communication system can beavoided.

Since the first modification of the tenth embodiment enables themodification and release of the MC configuration using the New AS layer,the optimal communication system can be built according to acommunication state of the whole system.

The embodiments and the modifications are merely illustrations of thepresent invention, and can be freely combined within the scope of thepresent invention. Any constituent elements of the embodiments and themodifications can be appropriately modified or omitted.

For example, the subframe in the embodiments and the modifications is anexample time unit of communication in the fifth generation base stationcommunication system. The subframe may be set per scheduling. Theprocesses described in the embodiments and the modifications as beingperformed per subframe may be performed per TTI, per slot, per sub-slot,or per mini-slot.

While the invention is described in detail, the foregoing description isin all aspects illustrative and does not restrict the present invention.Therefore, numerous modifications and variations that have not yet beenexemplified are devised without departing from the scope of the presentinvention.

DESCRIPTION OF REFERENCES

200 communication system, 202 communication terminal device, 203 basestation device.

1. (canceled)
 2. A communication system comprising: a user apparatus;and a base station including a distributed unit (DU) configured towirelessly communicate with the user apparatus and a central unit (CU)connected to the distributed unit, wherein the base station includingthe CU and the DU supports packet duplication, and the DU notifies theuser apparatus of starting the packet duplication.
 3. The communicationsystem according to claim 1, wherein the CU notifies the DU ofinformation related to starting the packet duplication, and the DUnotifies the user apparatus of starting the packet duplication by usinga MAC signaling.
 4. The communication system according to claim 1,wherein the DU notifies the CU of information related to a cell load andinformation related to a scheduling state.
 5. The communication systemaccording to claim 1, wherein the CU notifies the DU of informationrelated to whether or not the packet duplication is performed.
 6. A userapparatus in a communication system comprising the user apparatus; and abase station including a distributed unit (DU) configured to wirelesslycommunicate with the user apparatus and a central unit (CU) connected tothe distributed unit, wherein the base station including the CU and theDU supports packet duplication, and the user apparatus is notified ofstarting the packet duplication from the DU.
 7. A base station in acommunication system comprising a user apparatus; and the base stationincluding a distributed unit (DU) configured to wirelessly communicatewith the user apparatus and a central unit (CU) connected to thedistributed unit, wherein the base station including the CU and the DUsupports packet duplication, and the DU notifies the user apparatus ofstarting the packet duplication.